diff --git a/compiler/src/dmd/dcast.d b/compiler/src/dmd/dcast.d
index 8ab49b3c470f..55aa781f758a 100644
--- a/compiler/src/dmd/dcast.d
+++ b/compiler/src/dmd/dcast.d
@@ -1603,7 +1603,6 @@ MATCH implicitConvTo(Type from, Type to)
             // Disallow implicit conversion from complex to non-complex
             if (from.flags & TFlags.complex && !(tob.flags & TFlags.complex))
                 return MATCH.nomatch;
-
             // Disallow implicit conversion of real or imaginary to complex
             if (from.flags & (TFlags.real_ | TFlags.imaginary) && tob.flags & TFlags.complex)
                 return MATCH.nomatch;
@@ -1611,6 +1610,12 @@ MATCH implicitConvTo(Type from, Type to)
             // Disallow implicit conversion to-from real and imaginary
             if ((from.flags & (TFlags.real_ | TFlags.imaginary)) != (tob.flags & (TFlags.real_ | TFlags.imaginary)))
                 return MATCH.nomatch;
+            // Allow complex float to complex double promotion
+            if ((from.flags & TFlags.complex) && (tob.flags & TFlags.complex))
+            {
+                if (from.size(Loc.initial) < tob.size(Loc.initial))
+                    return MATCH.convert;
+            }
         }
         return MATCH.convert;
 
diff --git a/compiler/test/compilable/importc_complex_promotion.c b/compiler/test/compilable/importc_complex_promotion.c
new file mode 100644
index 000000000000..3271aa23a519
--- /dev/null
+++ b/compiler/test/compilable/importc_complex_promotion.c
@@ -0,0 +1,25 @@
+// Ensure complex float can be implicitly promoted to complex double
+// Fixes issue #22259
+#include <complex.h>
+
+void testComplexPromotion()
+{
+    _Complex float yf = 1.0if;
+    _Complex double x = yf;              // promotion: _Complex float -> _Complex double
+}
+
+void testComplexPreservation()
+{
+    // These should still work (no change)
+    _Complex float f1 = 1.0f + 1.0if;
+    _Complex float f2 = 1.0if + 2.0if;
+    _Complex double d1 = 1.0 + 2.0i;
+    _Complex double d2 = 2.0 + 3.0i;
+}
+
+int main()
+{
+    testComplexPromotion();
+    testComplexPreservation();
+    return 0;
+}