diff --git a/Makefile.am b/Makefile.am
index 99163c2c..3173ba99 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -50,6 +50,11 @@ if IS_SUNCC
 CFLAGS += -erroff=E_EMPTY_DECLARATION
 endif
 
+# Set _LINUX_SOURCE_COMPAT for AIX for mallocing 0 bytes
+if IS_AIX
+DEFS += -D_LINUX_SOURCE_COMPAT=1
+endif
+
 # List of sources.
 dist_tmux_SOURCES = \
 	arguments.c \