diff --git a/libc/fuzzing/stdlib/strtofloat_fuzz.cpp b/libc/fuzzing/stdlib/strtofloat_fuzz.cpp
--- a/libc/fuzzing/stdlib/strtofloat_fuzz.cpp
+++ b/libc/fuzzing/stdlib/strtofloat_fuzz.cpp
@@ -45,6 +45,17 @@
   if (str_ptr + size < out_ptr)
     __builtin_trap();
 
+  // If any of the outputs are NaN
+  if (atof_output != atof_output || strtof_output != strtof_output ||
+      strtod_output != strtod_output || strtold_output != strtold_output) {
+    // Then all the outputs should be NaN.
+    // This is a trivial check meant to silence the "unused variable" warnings.
+    if (atof_output == atof_output || strtof_output == strtof_output ||
+        strtod_output == strtod_output || strtold_output == strtold_output) {
+      __builtin_trap();
+    }
+  }
+
   delete[] container;
   return 0;
 }
diff --git a/libc/fuzzing/stdlib/strtointeger_fuzz.cpp b/libc/fuzzing/stdlib/strtointeger_fuzz.cpp
--- a/libc/fuzzing/stdlib/strtointeger_fuzz.cpp
+++ b/libc/fuzzing/stdlib/strtointeger_fuzz.cpp
@@ -65,6 +65,16 @@
   if (str_ptr + container_size - 1 < out_ptr)
     __builtin_trap();
 
+  // If atoi is non-zero and the base is at least 10
+  if (atoi_output != 0 && base >= 10) {
+    // Then all of the other functions should output non-zero values as well.
+    // This is a trivial check meant to silence the "unused variable" warnings.
+    if (atol_output == 0 || atoll_output == 0 || strtol_output == 0 ||
+        strtoll_output == 0 || strtoul_output == 0 || strtoull_output == 0) {
+      __builtin_trap();
+    }
+  }
+
   delete[] container;
   return 0;
 }