diff -uNr fluxbox-1.3.7/util/fbrun/FbRun.cc fluxbox-1.3.7.mod/util/fbrun/FbRun.cc
--- fluxbox-1.3.7/util/fbrun/FbRun.cc	2015-02-08 12:44:45.377187009 +0200
+++ fluxbox-1.3.7.mod/util/fbrun/FbRun.cc	2018-06-19 20:52:20.798391221 +0300
@@ -131,7 +131,7 @@
 
         const char *shell = getenv("SHELL");
         if (!shell)
-            shell = "/bin/sh";
+            shell = "@TERMUX_PREFIX@/bin/sh";
 
         setsid();
         execl(shell, shell, "-c", command.c_str(), static_cast<void*>(NULL));
