st.c | 3 +++

diff --git a/st.c b/st.c
index 693739e00f3f9110bbbf3f24931a7d64e7d9e872..43f5bc2aec13a24c5cacb37ee47610d51152fb09 100644
--- a/st.c
+++ b/st.c
@@ -865,6 +865,9 @@ execsh(void) {
 	char **args;
 	char *envshell = getenv("SHELL");
 
+	if (envshell == NULL)
+		envshell ="/bin/sh";
+
 	unsetenv("COLUMNS");
 	unsetenv("LINES");
 	unsetenv("TERMCAP");