diff --git a/lib/platform.cpp b/lib/platform.cpp
index 833c012ab8e..85614c6ea29 100644
--- a/lib/platform.cpp
+++ b/lib/platform.cpp
@@ -73,7 +73,7 @@ bool Platform::set(Type t)
         sizeof_wchar_t = 2;
         sizeof_size_t = 4;
         sizeof_pointer = 4;
-        defaultSign = '\0';
+        defaultSign = 's';
         char_bit = 8;
         calculateBitMembers();
         return true;
@@ -90,7 +90,7 @@ bool Platform::set(Type t)
         sizeof_wchar_t = 2;
         sizeof_size_t = 8;
         sizeof_pointer = 8;
-        defaultSign = '\0';
+        defaultSign = 's';
         char_bit = 8;
         calculateBitMembers();
         return true;
@@ -107,7 +107,7 @@ bool Platform::set(Type t)
         sizeof_wchar_t = 4;
         sizeof_size_t = 4;
         sizeof_pointer = 4;
-        defaultSign = '\0';
+        defaultSign = 's';
         char_bit = 8;
         calculateBitMembers();
         return true;
@@ -124,7 +124,7 @@ bool Platform::set(Type t)
         sizeof_wchar_t = 4;
         sizeof_size_t = 8;
         sizeof_pointer = 8;
-        defaultSign = '\0';
+        defaultSign = 's';
         char_bit = 8;
         calculateBitMembers();
         return true;
diff --git a/releasenotes.txt b/releasenotes.txt
index f130e957aec..e288b784a2e 100644
--- a/releasenotes.txt
+++ b/releasenotes.txt
@@ -19,3 +19,7 @@ Changed interface:
 
 Infrastructure & dependencies:
 -
+
+Other:
+- The built-in "win*" and "unix*" platforms will now default to signed char type instead of unknown signedness. If you require unsigned chars please specify "--funsigned-char"
+-
diff --git a/test/testplatform.cpp b/test/testplatform.cpp
index c0f7bb2c017..e29551463d3 100644
--- a/test/testplatform.cpp
+++ b/test/testplatform.cpp
@@ -85,7 +85,7 @@ class TestPlatform : public TestFixture {
         ASSERT_EQUALS(2, platform.sizeof_wchar_t);
         ASSERT_EQUALS(4, platform.sizeof_size_t);
         ASSERT_EQUALS(4, platform.sizeof_pointer);
-        ASSERT_EQUALS('\0', platform.defaultSign);
+        ASSERT_EQUALS('s', platform.defaultSign);
         ASSERT_EQUALS(8, platform.char_bit);
         ASSERT_EQUALS(16, platform.short_bit);
         ASSERT_EQUALS(32, platform.int_bit);
@@ -110,7 +110,7 @@ class TestPlatform : public TestFixture {
         ASSERT_EQUALS(4, platform.sizeof_wchar_t);
         ASSERT_EQUALS(8, platform.sizeof_size_t);
         ASSERT_EQUALS(8, platform.sizeof_pointer);
-        ASSERT_EQUALS('\0', platform.defaultSign);
+        ASSERT_EQUALS('s', platform.defaultSign);
         ASSERT_EQUALS(8, platform.char_bit);
         ASSERT_EQUALS(16, platform.short_bit);
         ASSERT_EQUALS(32, platform.int_bit);
@@ -138,7 +138,7 @@ class TestPlatform : public TestFixture {
         ASSERT_EQUALS(2, platform.sizeof_wchar_t);
         ASSERT_EQUALS(4, platform.sizeof_size_t);
         ASSERT_EQUALS(4, platform.sizeof_pointer);
-        ASSERT_EQUALS('\0', platform.defaultSign);
+        ASSERT_EQUALS('s', platform.defaultSign);
         ASSERT_EQUALS(8, platform.char_bit);
         ASSERT_EQUALS(16, platform.short_bit);
         ASSERT_EQUALS(32, platform.int_bit);
@@ -166,7 +166,7 @@ class TestPlatform : public TestFixture {
         ASSERT_EQUALS(4, platform.sizeof_wchar_t);
         ASSERT_EQUALS(4, platform.sizeof_size_t);
         ASSERT_EQUALS(4, platform.sizeof_pointer);
-        ASSERT_EQUALS('\0', platform.defaultSign);
+        ASSERT_EQUALS('s', platform.defaultSign);
         ASSERT_EQUALS(8, platform.char_bit);
         ASSERT_EQUALS(16, platform.short_bit);
         ASSERT_EQUALS(32, platform.int_bit);
@@ -194,7 +194,7 @@ class TestPlatform : public TestFixture {
         ASSERT_EQUALS(2, platform.sizeof_wchar_t);
         ASSERT_EQUALS(8, platform.sizeof_size_t);
         ASSERT_EQUALS(8, platform.sizeof_pointer);
-        ASSERT_EQUALS('\0', platform.defaultSign);
+        ASSERT_EQUALS('s', platform.defaultSign);
         ASSERT_EQUALS(8, platform.char_bit);
         ASSERT_EQUALS(16, platform.short_bit);
         ASSERT_EQUALS(32, platform.int_bit);
diff --git a/test/testtype.cpp b/test/testtype.cpp
index bf36182c59a..b8cfae820d5 100644
--- a/test/testtype.cpp
+++ b/test/testtype.cpp
@@ -103,16 +103,16 @@ class TestType : public TestFixture {
         // unsigned types getting promoted to int sizeof(int) = 4 bytes
         // and unsigned types having already a size of 4 bytes
         {
-            const std::string types[] = {"unsigned char", /*[unsigned]*/ "char", "bool", "unsigned short", "unsigned int", "unsigned long"};
+            const std::string types[] = {"unsigned char", "bool", "unsigned short", "unsigned int", "unsigned long"};
             for (const std::string& type : types) {
                 check(type + " f(" + type +" x) { return x << 31; }", dinit(CheckOptions, $.settings = &settings));
-                ASSERT_EQUALS("", errout_str());
+                ASSERT_EQUALS_MSG("", errout_str(), type);
                 check(type + " f(" + type +" x) { return x << 33; }", dinit(CheckOptions, $.settings = &settings));
-                ASSERT_EQUALS("[test.cpp:1]: (error) Shifting 32-bit value by 33 bits is undefined behaviour\n", errout_str());
+                ASSERT_EQUALS_MSG("[test.cpp:1]: (error) Shifting 32-bit value by 33 bits is undefined behaviour\n", errout_str(), type);
                 check(type + " f(int x) { return (x = (" + type + ")x << 32); }", dinit(CheckOptions, $.settings = &settings));
-                ASSERT_EQUALS("[test.cpp:1]: (error) Shifting 32-bit value by 32 bits is undefined behaviour\n", errout_str());
+                ASSERT_EQUALS_MSG("[test.cpp:1]: (error) Shifting 32-bit value by 32 bits is undefined behaviour\n", errout_str(), type);
                 check(type + " foo(" + type + " x) { return x << 31; }", dinit(CheckOptions, $.settings = &settings));
-                ASSERT_EQUALS("", errout_str());
+                ASSERT_EQUALS_MSG("", errout_str(), type);
             }
         }
         // signed types getting promoted to int sizeof(int) = 4 bytes