diff --git a/src/kernel/reports_test.c b/src/kernel/reports_test.c
index c3ee0c3c1..0bfa47e34 100644
--- a/src/kernel/reports_test.c
+++ b/src/kernel/reports_test.c
@@ -62,16 +62,16 @@ static void test_regionid(CuTest * tc) {
   plain = test_create_terrain("plain", 0);
   r = test_create_region(0, 0, plain);
 
-  memset(buffer, 0xff, sizeof(buffer));
+  memset(buffer, -2, sizeof(buffer));
   len = f_regionid(r, 0, buffer, sizeof(buffer));
   CuAssertIntEquals(tc, 11, len);
   CuAssertStrEquals(tc, "plain (0,0)", buffer);
 
-  memset(buffer, -1, sizeof(buffer));
+  memset(buffer, -2, sizeof(buffer));
   len = f_regionid(r, 0, buffer, 11);
   CuAssertIntEquals(tc, 10, len);
   CuAssertStrEquals(tc, "plain (0,0", buffer);
-  CuAssertIntEquals(tc, -1, buffer[11]);
+  CuAssertIntEquals(tc, (char)-2, buffer[11]);
 }
 
 CuSuite *get_reports_suite(void)
diff --git a/src/util/bsdstring_test.c b/src/util/bsdstring_test.c
index 25e7be60d..0f9cdaeac 100644
--- a/src/util/bsdstring_test.c
+++ b/src/util/bsdstring_test.c
@@ -15,11 +15,11 @@ static void test_strlcat(CuTest * tc)
   buffer[0] = '\0';
   CuAssertIntEquals(tc, 4, strlcat(buffer, "herp", 8));
   CuAssertStrEquals(tc, "herp", buffer);
-  CuAssertIntEquals(tc, -2, buffer[5]);
+  CuAssertIntEquals(tc, (char)-2, buffer[5]);
 
   CuAssertIntEquals(tc, 8, strlcat(buffer, "derp", 8));
   CuAssertStrEquals(tc, "herpder", buffer);
-  CuAssertIntEquals(tc, -2, buffer[8]);
+  CuAssertIntEquals(tc, (char)-2, buffer[8]);
 }
 
 static void test_strlcpy(CuTest * tc)
@@ -33,11 +33,11 @@ static void test_strlcpy(CuTest * tc)
 
   CuAssertIntEquals(tc, 4, strlcpy(buffer, "herp", 8));
   CuAssertStrEquals(tc, "herp", buffer);
-  CuAssertIntEquals(tc, -2, buffer[5]);
+  CuAssertIntEquals(tc, (char)-2, buffer[5]);
 
   CuAssertIntEquals(tc, 8, strlcpy(buffer, "herpderp", 8));
   CuAssertStrEquals(tc, "herpder", buffer);
-  CuAssertIntEquals(tc, -2, buffer[8]);
+  CuAssertIntEquals(tc, (char)-2, buffer[8]);
 }
 
 static void test_slprintf(CuTest * tc)
@@ -51,11 +51,11 @@ static void test_slprintf(CuTest * tc)
 
   CuAssertIntEquals(tc, 4, slprintf(buffer, 8, "%s", "herp"));
   CuAssertStrEquals(tc, "herp", buffer);
-  CuAssertIntEquals(tc, -2, buffer[5]);
+  CuAssertIntEquals(tc, (char)-2, buffer[5]);
 
   CuAssertIntEquals(tc, 8, slprintf(buffer, 8, "%s", "herpderp"));
   CuAssertStrEquals(tc, "herpder", buffer);
-  CuAssertIntEquals(tc, -2, buffer[8]);
+  CuAssertIntEquals(tc, (char)-2, buffer[8]);
 }
 
 CuSuite *get_bsdstring_suite(void)