diff --git a/Lib/_osx_support.py b/Lib/_osx_support.py
index 5a0b71e..d02b885 100644
--- a/Lib/_osx_support.py
+++ b/Lib/_osx_support.py
@@ -182,7 +182,7 @@
         # Compiler is GCC, check if it is LLVM-GCC
         data = _read_output("'%s' --version"
                              % (cc.replace("'", "'\"'\"'"),))
-        if 'llvm-gcc' in data:
+        if data and 'llvm-gcc' in data:
             # Found LLVM-GCC, fall back to clang
             cc = _find_build_tool('clang')
 
diff --git a/Misc/ACKS b/Misc/ACKS
index 3af3ff4..9a6f57a 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1280,6 +1280,7 @@
 Paul Swartz
 Thenault Sylvain
 Péter Szabó
+John Szakmeister
 Amir Szekely
 Arfrever Frehtes Taifersar Arahesis
 Hideaki Takahashi
diff --git a/Misc/NEWS b/Misc/NEWS
index 4c0c3a6..54546b4 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -271,6 +271,9 @@
   (Original patches by Hirokazu Yamamoto and Amaury Forgeot d'Arc, with
   suggested wording by David Gutteridge)
 
+- Issue #21311: Avoid exception in _osx_support with non-standard compiler
+  configurations.  Patch by John Szakmeister.
+
 Tools/Demos
 -----------