diff --git a/absl/strings/str_format_test.cc b/absl/strings/str_format_test.cc
index 969e1f9e..3f265d19 100644
--- a/absl/strings/str_format_test.cc
+++ b/absl/strings/str_format_test.cc
@@ -516,14 +516,11 @@ TEST_F(FormatEntryPointTest, SNPrintF) {
   EXPECT_EQ(result, 17);
   EXPECT_EQ(std::string(buffer), "NUMBER: 1234567");
 
-  // The `output` parameter is annotated nonnull, but we want to test that
-  // it is never written to if the size is zero.
-  // Use a variable instead of passing nullptr directly to avoid a `-Wnonnull`
-  // warning.
-  char* null_output = nullptr;
-  result =
-      SNPrintF(null_output, 0, "Just checking the %s of the output.", "size");
+  // Test that the buffer is never written to if the size is zero.
+  buffer[0] = '\0';
+  result = SNPrintF(buffer, 0, "Just checking the %s of the output.", "size");
   EXPECT_EQ(result, 37);
+  EXPECT_EQ(buffer[0], '\0');
 }
 
 TEST_F(FormatEntryPointTest, SNPrintFWithV) {
@@ -551,14 +548,11 @@ TEST_F(FormatEntryPointTest, SNPrintFWithV) {
 
   std::string size = "size";
 
-  // The `output` parameter is annotated nonnull, but we want to test that
-  // it is never written to if the size is zero.
-  // Use a variable instead of passing nullptr directly to avoid a `-Wnonnull`
-  // warning.
-  char* null_output = nullptr;
-  result =
-      SNPrintF(null_output, 0, "Just checking the %v of the output.", size);
+  // Test that the buffer is never written to if the size is zero.
+  buffer[0] = '\0';
+  result = SNPrintF(buffer, 0, "Just checking the %v of the output.", size);
   EXPECT_EQ(result, 37);
+  EXPECT_EQ(buffer[0], '\0');
 }
 
 TEST(StrFormat, BehavesAsDocumented) {