diff --git a/config.gnu.mk b/config.gnu.mk
index e3596a9..c32ae76 100644
--- a/config.gnu.mk
+++ b/config.gnu.mk
@@ -90,3 +90,4 @@ CONFIG_FLAGS=$(shell grep '// [A-Z]*FLAGS=' "$<" | sed -e 's|// [A-Z]*FLAGS=||g'
 CC_CONFIG=	mkdir -p "$$(dirname "$@")" ; echo '\#define' HAVE_$(CONFIG_UPPER)_H $(shell $(CC) $(CFLAGS) $(CFLAGS_CONFIG_$*) $(CONFIG_FLAGS) "$<" -o "$<".exe > "$<".err 2>&1 && "$<".exe > "$<".out && echo 1 || echo 0) | sed -e 's|\#define \(.*\) 0|/* \#undef \1 */|g' > "$@"; [ -f "$<".out ] && cat >> "$@" "$<".out; true
 CXX_CONFIG=	mkdir -p "$$(dirname "$@")" ; echo '\#define' HAVE_$(CONFIG_UPPER) $(shell $(CXX) $(CXXFLAGS) $(CXXFLAGS_CONFIG_$*) $(CONFIG_FLAGS) "$<" -o "$<".exe > "$<".err 2>&1 && "$<".exe > "$<".out && echo 1 || echo 0) | sed -e 's|\#define \(.*\) 0|/* \#undef \1 */|g' > "$@"; [ -f "$<".out ] && cat >> "$@" "$<".out; true
 LIB_CONFIG=	mkdir -p "$$(dirname "$@")" ; echo '\#define HAVE_LIB'$(CONFIG_UPPER) $$($(CC) $(CCFLAGS) $(CFLAGS_CONFIG_$*) -l$* "$<" -o "$<".exe > "$<".err 2>&1 && "$<".exe && echo 1 || echo 0) | sed -e 's|\#define \(.*\) 0|/* \#undef \1 */|g' > "$@"
+FN_CONFIG=	mkdir -p "$$(dirname "$@")" ; echo '\#define HAVE_'$(CONFIG_UPPER) $$($(CC) $(CCFLAGS) $(CFLAGS_CONFIG_$*) "$<" -o "$<".exe > "$<".err 2>&1 && "$<".exe && echo 1 || echo 0) | sed -e 's|\#define \(.*\) 0|/* \#undef \1 */|g' > "$@"
diff --git a/rules.mk b/rules.mk
index 828c331..f0ed160 100644
--- a/rules.mk
+++ b/rules.mk
@@ -392,8 +392,8 @@ $(OBJDIR)/CONFIG_LIB%.c:
 
 # Check if a function is present
 $(OBJDIR)/HAVE_%: $(OBJDIR)/CONFIG_CHECK_%.c
-	$(PRINT_CONFIG)	$(CC_CONFIG)
-$(OBJDIR)/CONFIG_CHECK_%.c: config/check_%.c
+	$(PRINT_CONFIG)	$(FN_CONFIG)
+$(OBJDIR)/CONFIG_CHECK_%.c: $(BUILD)config/check_%.c
 	$(PRINT_COPY) cp $< $@