diff --git a/vlib/v/checker/comptime.v b/vlib/v/checker/comptime.v
index 78e67c6c47..e925fc4382 100644
--- a/vlib/v/checker/comptime.v
+++ b/vlib/v/checker/comptime.v
@@ -381,19 +381,25 @@ fn (mut c Checker) evaluate_once_comptime_if_attribute(mut node ast.Attr) bool {
 		}
 	}
 	c.inside_ct_attr = true
-	node.ct_skip = c.comptime_if_branch(node.ct_expr, node.pos)
+	node.ct_skip = if c.comptime_if_branch(node.ct_expr, node.pos) == .skip { true } else { false }
 	c.inside_ct_attr = false
 	node.ct_evaled = true
 	return node.ct_skip
 }
 
+enum ComptimeBranchSkipState {
+	eval
+	skip
+	unknown
+}
+
 // comptime_if_branch checks the condition of a compile-time `if` branch. It returns `true`
 // if that branch's contents should be skipped (targets a different os for example)
-fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) bool {
+fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) ComptimeBranchSkipState {
 	// TODO: better error messages here
 	match cond {
 		ast.BoolLiteral {
-			return !cond.val
+			return if cond.val { .eval } else { .skip }
 		}
 		ast.ParExpr {
 			return c.comptime_if_branch(cond.expr, pos)
@@ -402,13 +408,20 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) bool {
 			if cond.op != .not {
 				c.error('invalid `\$if` condition', cond.pos)
 			}
-			return !c.comptime_if_branch(cond.right, cond.pos)
+			reversed := c.comptime_if_branch(cond.right, cond.pos)
+			return if reversed == .eval {
+				.skip
+			} else if reversed == .skip {
+				.eval
+			} else {
+				reversed
+			}
 		}
 		ast.PostfixExpr {
 			if cond.op != .question {
 				c.error('invalid \$if postfix operator', cond.pos)
 			} else if cond.expr is ast.Ident {
-				return cond.expr.name !in c.pref.compile_defines_all
+				return if cond.expr.name in c.pref.compile_defines_all { .eval } else { .skip }
 			} else {
 				c.error('invalid `\$if` condition', cond.pos)
 			}
@@ -418,12 +431,18 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) bool {
 				.and {
 					l := c.comptime_if_branch(cond.left, cond.pos)
 					r := c.comptime_if_branch(cond.right, cond.pos)
-					return l || r // skip (return true) if at least one should be skipped
+					if l == .unknown || r == .unknown {
+						return .unknown
+					}
+					return if l == .eval && r == .eval { .eval } else { .skip }
 				}
 				.logical_or {
 					l := c.comptime_if_branch(cond.left, cond.pos)
 					r := c.comptime_if_branch(cond.right, cond.pos)
-					return l && r // skip (return true) only if both should be skipped
+					if l == .unknown || r == .unknown {
+						return .unknown
+					}
+					return if l == .eval || r == .eval { .eval } else { .skip }
 				}
 				.key_is, .not_is {
 					if cond.left is ast.TypeNode && cond.right is ast.TypeNode {
@@ -433,15 +452,19 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) bool {
 							c.expr(cond.left)
 							// c.error('`$sym.name` is not an interface', cond.right.pos())
 						}
-						return false
+						return .unknown
 					} else if cond.left is ast.TypeNode && cond.right is ast.ComptimeType {
 						left := cond.left as ast.TypeNode
 						checked_type := c.unwrap_generic(left.typ)
-						return c.table.is_comptime_type(checked_type, cond.right)
+						return if c.table.is_comptime_type(checked_type, cond.right) {
+							.eval
+						} else {
+							.skip
+						}
 					} else if cond.left in [ast.SelectorExpr, ast.TypeNode] {
 						// `$if method.@type is string`
 						c.expr(cond.left)
-						return false
+						return .unknown
 					} else {
 						c.error('invalid `\$if` condition: expected a type or a selector expression or an interface check',
 							cond.left.pos())
@@ -456,7 +479,7 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) bool {
 						right_type := c.expr(cond.right)
 						expr := c.find_definition(cond.left) or {
 							c.error(err.msg(), cond.left.pos)
-							return false
+							return .unknown
 						}
 						if !c.check_types(right_type, left_type) {
 							left_name := c.table.type_to_str(left_type)
@@ -467,7 +490,19 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) bool {
 						// :)
 						// until `v.eval` is stable, I can't think of a better way to do this
 						different := expr.str() != cond.right.str()
-						return if cond.op == .eq { different } else { !different }
+						return if cond.op == .eq {
+							if different {
+								ComptimeBranchSkipState.skip
+							} else {
+								ComptimeBranchSkipState.eval
+							}
+						} else {
+							if different {
+								ComptimeBranchSkipState.eval
+							} else {
+								ComptimeBranchSkipState.skip
+							}
+						}
 					} else {
 						c.error('invalid `\$if` condition: ${cond.left.type_name()}1',
 							cond.pos)
@@ -481,51 +516,81 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) bool {
 		ast.Ident {
 			cname := cond.name
 			if cname in valid_comptime_if_os {
-				mut is_os_target_different := false
+				mut is_os_target_equal := true
 				if !c.pref.output_cross_c {
 					target_os := c.pref.os.str().to_lower()
-					is_os_target_different = cname != target_os
+					is_os_target_equal = cname == target_os
 				}
-				return is_os_target_different
+				return if is_os_target_equal { .eval } else { .skip }
 			} else if cname in valid_comptime_if_compilers {
-				return pref.cc_from_string(cname) != c.pref.ccompiler_type
+				return if pref.cc_from_string(cname) == c.pref.ccompiler_type {
+					.eval
+				} else {
+					.skip
+				}
 			} else if cname in valid_comptime_if_platforms {
 				if cname == 'aarch64' {
 					c.note('use `arm64` instead of `aarch64`', pos)
 				}
 				match cname {
-					'amd64' { return c.pref.arch != .amd64 }
-					'i386' { return c.pref.arch != .i386 }
-					'aarch64' { return c.pref.arch != .arm64 }
-					'arm64' { return c.pref.arch != .arm64 }
-					'arm32' { return c.pref.arch != .arm32 }
-					'rv64' { return c.pref.arch != .rv64 }
-					'rv32' { return c.pref.arch != .rv32 }
-					else { return false }
+					'amd64' { return if c.pref.arch == .amd64 { .eval } else { .skip } }
+					'i386' { return if c.pref.arch == .i386 { .eval } else { .skip } }
+					'aarch64' { return if c.pref.arch == .arm64 { .eval } else { .skip } }
+					'arm64' { return if c.pref.arch == .arm64 { .eval } else { .skip } }
+					'arm32' { return if c.pref.arch == .arm32 { .eval } else { .skip } }
+					'rv64' { return if c.pref.arch == .rv64 { .eval } else { .skip } }
+					'rv32' { return if c.pref.arch == .rv32 { .eval } else { .skip } }
+					else { return .unknown }
 				}
 			} else if cname in valid_comptime_if_cpu_features {
-				return false
+				return .unknown
 			} else if cname in valid_comptime_if_other {
 				match cname {
-					'apk' { return !c.pref.is_apk }
-					'js' { return !c.pref.backend.is_js() }
-					'debug' { return !c.pref.is_debug }
-					'prod' { return !c.pref.is_prod }
-					'profile' { return !c.pref.is_prof }
-					'test' { return !c.pref.is_test }
-					'glibc' { return false } // TODO
-					'threads' { return c.table.gostmts == 0 }
-					'prealloc' { return !c.pref.prealloc }
-					'no_bounds_checking' { return cname !in c.pref.compile_defines_all }
-					'freestanding' { return !c.pref.is_bare || c.pref.output_cross_c }
-					'interpreter' { c.pref.backend != .interpret }
-					else { return false }
+					'apk' {
+						return if c.pref.is_apk { .eval } else { .skip }
+					}
+					'js' {
+						return if c.pref.backend.is_js() { .eval } else { .skip }
+					}
+					'debug' {
+						return if c.pref.is_debug { .eval } else { .skip }
+					}
+					'prod' {
+						return if c.pref.is_prod { .eval } else { .skip }
+					}
+					'profile' {
+						return if c.pref.is_prof { .eval } else { .skip }
+					}
+					'test' {
+						return if c.pref.is_test { .eval } else { .skip }
+					}
+					'glibc' {
+						return .unknown
+					} // TODO
+					'threads' {
+						return if c.table.gostmts > 0 { .eval } else { .skip }
+					}
+					'prealloc' {
+						return if c.pref.prealloc { .eval } else { .skip }
+					}
+					'no_bounds_checking' {
+						return if cname in c.pref.compile_defines_all { .eval } else { .skip }
+					}
+					'freestanding' {
+						return if c.pref.is_bare && !c.pref.output_cross_c { .eval } else { .skip }
+					}
+					'interpreter' {
+						return if c.pref.backend == .interpret { .eval } else { .skip }
+					}
+					else {
+						return .unknown
+					}
 				}
 			} else if cname !in c.pref.compile_defines_all {
 				if cname == 'linux_or_macos' {
 					c.error('linux_or_macos is deprecated, use `\$if linux || macos {` instead',
 						cond.pos)
-					return false
+					return .unknown
 				}
 				// `$if some_var {}`, or `[if user_defined_tag] fn abc(){}`
 				typ := c.unwrap_generic(c.expr(cond))
@@ -534,11 +599,11 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) bool {
 					if !c.inside_ct_attr {
 						c.error('unknown var: `$cname`', pos)
 					}
-					return false
+					return .unknown
 				}
 				expr := c.find_obj_definition(cond.obj) or {
 					c.error(err.msg(), cond.pos)
-					return false
+					return .unknown
 				}
 				if !c.check_types(typ, ast.bool_type) {
 					type_name := c.table.type_to_str(typ)
@@ -546,21 +611,22 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Pos) bool {
 				}
 				// :)
 				// until `v.eval` is stable, I can't think of a better way to do this
-				return !(expr as ast.BoolLiteral).val
+				return if (expr as ast.BoolLiteral).val { .eval } else { .skip }
 			}
 		}
 		ast.ComptimeCall {
 			if cond.is_pkgconfig {
 				mut m := pkgconfig.main([cond.args_var]) or {
 					c.error(err.msg(), cond.pos)
-					return true
+					return .skip
 				}
-				m.run() or { return true }
+				m.run() or { return .skip }
 			}
+			return .eval
 		}
 		else {
 			c.error('invalid `\$if` condition', pos)
 		}
 	}
-	return false
+	return .unknown
 }
diff --git a/vlib/v/checker/if.v b/vlib/v/checker/if.v
index bc2613e10a..05648fb399 100644
--- a/vlib/v/checker/if.v
+++ b/vlib/v/checker/if.v
@@ -30,7 +30,7 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 	node.typ = ast.void_type
 	mut nbranches_with_return := 0
 	mut nbranches_without_return := 0
-	mut should_skip := false // Whether the current branch should be skipped
+	mut skip_state := ComptimeBranchSkipState.unknown
 	mut found_branch := false // Whether a matching branch was found- skip the rest
 	mut is_comptime_type_is_expr := false // if `$if T is string`
 	for i in 0 .. node.branches.len {
@@ -41,8 +41,8 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 		}
 		if !node.has_else || i < node.branches.len - 1 {
 			if node.is_comptime {
-				should_skip = c.comptime_if_branch(branch.cond, branch.pos)
-				node.branches[i].pkg_exist = !should_skip
+				skip_state = c.comptime_if_branch(branch.cond, branch.pos)
+				node.branches[i].pkg_exist = if skip_state == .eval { true } else { false }
 			} else {
 				// check condition type is boolean
 				c.expected_type = ast.bool_type
@@ -67,7 +67,11 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 					if branch.cond.right is ast.ComptimeType && left is ast.TypeNode {
 						is_comptime_type_is_expr = true
 						checked_type := c.unwrap_generic(left.typ)
-						should_skip = !c.table.is_comptime_type(checked_type, branch.cond.right as ast.ComptimeType)
+						skip_state = if c.table.is_comptime_type(checked_type, branch.cond.right as ast.ComptimeType) {
+							.eval
+						} else {
+							.skip
+						}
 					} else {
 						got_type := c.unwrap_generic((branch.cond.right as ast.TypeNode).typ)
 						sym := c.table.sym(got_type)
@@ -84,14 +88,17 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 							is_comptime_type_is_expr = true
 							// is interface
 							checked_type := c.unwrap_generic(left.typ)
-							should_skip = !c.table.does_type_implement_interface(checked_type,
+							skip_state = if c.table.does_type_implement_interface(checked_type,
 								got_type)
+							{
+								.eval
+							} else {
+								.skip
+							}
 						} else if left is ast.TypeNode {
 							is_comptime_type_is_expr = true
 							left_type := c.unwrap_generic(left.typ)
-							if left_type != got_type {
-								should_skip = true
-							}
+							skip_state = if left_type == got_type { .eval } else { .skip }
 						}
 					}
 				}
@@ -99,10 +106,10 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 			cur_skip_flags := c.skip_flags
 			if found_branch {
 				c.skip_flags = true
-			} else if should_skip {
+			} else if skip_state == .skip {
 				c.skip_flags = true
-				should_skip = false // Reset the value of `should_skip` for the next branch
-			} else if !is_comptime_type_is_expr {
+				skip_state = .unknown // Reset the value of `skip_state` for the next branch
+			} else if !is_comptime_type_is_expr && skip_state == .eval {
 				found_branch = true // If a branch wasn't skipped, the rest must be
 			}
 			if c.fn_level == 0 && c.pref.output_cross_c {
diff --git a/vlib/v/gen/c/testdata/comp_if_unknown.c.must_have b/vlib/v/gen/c/testdata/comp_if_unknown.c.must_have
new file mode 100644
index 0000000000..e32240c61d
--- /dev/null
+++ b/vlib/v/gen/c/testdata/comp_if_unknown.c.must_have
@@ -0,0 +1,5 @@
+#if defined(__GLIBC__)
+x = 2;
+#else
+x = 3;
+#endif
diff --git a/vlib/v/gen/c/testdata/comp_if_unknown.vv b/vlib/v/gen/c/testdata/comp_if_unknown.vv
new file mode 100644
index 0000000000..a1fdbab1e4
--- /dev/null
+++ b/vlib/v/gen/c/testdata/comp_if_unknown.vv
@@ -0,0 +1,9 @@
+fn main() {
+	mut x := 1
+	$if glibc {
+		x = 2
+	} $else {
+		x = 3
+	}
+	println('done')
+}