diff --git a/test/api.cpp b/test/api.cpp
index 880fa25c..c4ccb2f6 100644
--- a/test/api.cpp
+++ b/test/api.cpp
@@ -56,8 +56,8 @@ int main()
   std::cout << "pi(" << in << ") = " << out;
   check(out == "0");
 
-  // Test using INT128_MIN
-  in = "-170141183460469231731687303715884105728";
+  // Test using INT128_MIN+1
+  in = "-170141183460469231731687303715884105727";
   out = pi(in);
   std::cout << "pi(" << in << ") = " << out;
   check(out == "0");  
diff --git a/test/api_c.c b/test/api_c.c
index 3de64fa9..0e5d9bee 100644
--- a/test/api_c.c
+++ b/test/api_c.c
@@ -58,9 +58,9 @@ int main(void)
     printf("primecount_pi_str(-1208925819614629174696176) = %s", out);
     check(strcmp(out, "0") == 0);
 
-    // Test using INT128_MIN
-    primecount_pi_str("-170141183460469231731687303715884105728", out, sizeof(out));
-    printf("primecount_pi_str(-170141183460469231731687303715884105728) = %s", out);
+    // Test using INT128_MIN+1
+    primecount_pi_str("-170141183460469231731687303715884105727", out, sizeof(out));
+    printf("primecount_pi_str(-170141183460469231731687303715884105727) = %s", out);
     check(strcmp(out, "0") == 0);
   }