diff --git a/Makefile.am b/Makefile.am
index 9fa84e29..b338bb9d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -189,7 +189,7 @@ endif
 
 if BUILD_C_API
 lib_LTLIBRARIES = libprofanity.la
-libprofanity_la_LDFLAGS=-avoid-version -shared
+libprofanity_la_LDFLAGS=-avoid-version -shared -no-undefined
 libprofanity_la_SOURCES = src/plugins/profapi.c
 
 library_includedir=$(includedir)
diff --git a/src/ui/mucwin.c b/src/ui/mucwin.c
index e3826eb1..4d323ef1 100644
--- a/src/ui/mucwin.c
+++ b/src/ui/mucwin.c
@@ -32,6 +32,8 @@
  *
  */
 
+#define _GNU_SOURCE 1
+
 #include <string.h>
 #include <assert.h>
 #include <stdlib.h>