diff --git a/src/interfaces/libpq/Makefile b/src/interfaces/libpq/Makefile
index 921adf47e82..9e5db9d1601 100644
--- a/src/interfaces/libpq/Makefile
+++ b/src/interfaces/libpq/Makefile
@@ -112,13 +112,13 @@ install: all installdirs install-lib
 	$(INSTALL_DATA) $(srcdir)/libpq-int.h '$(DESTDIR)$(includedir_internal)'
 	$(INSTALL_DATA) $(srcdir)/pqexpbuffer.h '$(DESTDIR)$(includedir_internal)'
 	$(INSTALL_DATA) $(srcdir)/pg_service.conf.sample '$(DESTDIR)$(datadir)/pg_service.conf.sample'
-ifneq (,$findstring($(PORTNAME), win32 cygwin))
+ifneq (,$(findstring $(PORTNAME), win32 cygwin))
 	$(INSTALL_DATA) $(shlib) '$(DESTDIR)$(bindir)/$(shlib)'
 endif
 
 installdirs: installdirs-lib
 	$(MKDIR_P) '$(DESTDIR)$(includedir)' '$(DESTDIR)$(includedir_internal)'
-ifneq (,$findstring($(PORTNAME), win32 cygwin))
+ifneq (,$(findstring $(PORTNAME), win32 cygwin))
 	$(MKDIR_P) '$(DESTDIR)$(bindir)'
 endif
 
@@ -128,7 +128,7 @@ uninstall: uninstall-lib
 	rm -f '$(DESTDIR)$(includedir_internal)/libpq-int.h'
 	rm -f '$(DESTDIR)$(includedir_internal)/pqexpbuffer.h'
 	rm -f '$(DESTDIR)$(datadir)/pg_service.conf.sample'
-ifneq (,$findstring($(PORTNAME), win32 cygwin))
+ifneq (,$(findstring $(PORTNAME), win32 cygwin))
 	rm -f '$(DESTDIR)$(bindir)/$(shlib)'
 endif