diff --git a/external/firebird/UnpackedTarball_firebird.mk b/external/firebird/UnpackedTarball_firebird.mk
index 0233ce24dbf4..1f76870b8d18 100644
--- a/external/firebird/UnpackedTarball_firebird.mk
+++ b/external/firebird/UnpackedTarball_firebird.mk
@@ -50,6 +50,7 @@ $(eval $(call gb_UnpackedTarball_add_patches,firebird,\
     external/firebird/wnt-per-process-trace-storage.patch.1 \
     external/firebird/0001-extern-cloop-Missing-dependencies-of-compilations-on.patch.1 \
     external/firebird/configure-c99.patch \
+    external/firebird/Wincompatible-function-pointer-types.patch \
 ))
 
 ifeq ($(OS),WNT)
diff --git a/external/firebird/Wincompatible-function-pointer-types.patch b/external/firebird/Wincompatible-function-pointer-types.patch
new file mode 100755
index 000000000000..d5482bdcf2c2
--- /dev/null
+++ b/external/firebird/Wincompatible-function-pointer-types.patch
@@ -0,0 +1,11 @@
+--- extern/cloop/src/tests/test1/CTest.c
++++ extern/cloop/src/tests/test1/CTest.c
+@@ -402,7 +402,7 @@
+ 	struct CALC_IFactory* (*createFactory)();
+ 
+ #ifdef WIN32
+-	createFactory = (struct Factory* (*)()) GetProcAddress(library, "createFactory");
++	createFactory = (struct CALC_IFactory* (*)()) GetProcAddress(library, "createFactory");
+ #else
+ 	createFactory = dlsym(library, "createFactory");
+ #endif