diff --git a/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp
--- a/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/NotNullTerminatedResultCheck.cpp
@@ -805,10 +805,12 @@
         // PP->getMacroInfo() returns nullptr if macro has no definition.
         if (MI) {
           const auto &T = MI->tokens().back();
-          StringRef ValueStr = StringRef(T.getLiteralData(), T.getLength());
-          llvm::APInt IntValue;
-          ValueStr.getAsInteger(10, IntValue);
-          AreSafeFunctionsWanted = IntValue.getZExtValue();
+          if (T.isLiteral() && T.getLiteralData()) {
+            StringRef ValueStr = StringRef(T.getLiteralData(), T.getLength());
+            llvm::APInt IntValue;
+            ValueStr.getAsInteger(10, IntValue);
+            AreSafeFunctionsWanted = IntValue.getZExtValue();
+          }
         }
       }
 
diff --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone-not-null-terminated-result-stdc-want-lib-ext1-not-a-literal.c b/clang-tools-extra/test/clang-tidy/checkers/bugprone-not-null-terminated-result-stdc-want-lib-ext1-not-a-literal.c
new file mode 100644
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone-not-null-terminated-result-stdc-want-lib-ext1-not-a-literal.c
@@ -0,0 +1,16 @@
+// RUN: %check_clang_tidy %s bugprone-not-null-terminated-result %t -- \
+// RUN: -- -std=c11 -I %S/Inputs/bugprone-not-null-terminated-result
+
+#include "not-null-terminated-result-c.h"
+
+#define __STDC_LIB_EXT1__ 1
+#define __STDC_WANT_LIB_EXT1__ ((unsigned)1)
+
+void f(const char *src) {
+  char dest[13];
+  memcpy_s(dest, 13, src, strlen(src) - 1);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: the result from calling 'memcpy_s' is not null-terminated [bugprone-not-null-terminated-result]
+  // CHECK-FIXES: char dest[14];
+  // CHECK-FIXES-NEXT: strncpy_s(dest, 14, src, strlen(src) - 1);
+}
+