diff --git a/.travis.yml b/.travis.yml
index 600cf305..37cf2eca 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -25,7 +25,6 @@ addons:
   homebrew:
     packages:
       - autoconf-archive
-    update: true
 
 env:
   global:
@@ -110,13 +109,12 @@ matrix:
   # macOS
   #
   - os: osx
-    osx_image: xcode8
+    osx_image: xcode11
     env:
       - TEST="macOS"
-      - MATRIX_EVAL="brew install gcc && CC=gcc-7 && CXX=g++-7"
     before_install:
-      - eval "${MATRIX_EVAL}"
       - uname -a
+      - g++ --version
     script:
       - autoreconf -v --install --force
       - ./configure --prefix=/usr
diff --git a/src/fstring.cpp b/src/fstring.cpp
index ab4c24db..d92aea0d 100644
--- a/src/fstring.cpp
+++ b/src/fstring.cpp
@@ -779,7 +779,7 @@ FString& FString::setNumber (sInt64 num)
   uInt64 abs_num = static_cast<uInt64>(num);
 
   if ( num < 0 )
-    abs_num = -num;
+    abs_num = static_cast<uInt64>(-num);
 
   *s = '\0';
 
@@ -858,7 +858,7 @@ FString& FString::setFormatedNumber (sInt64 num, char separator)
     separator = ' ';
 
   if ( num < 0 )
-    abs_num = -num;
+    abs_num = static_cast<uInt64>(-num);
 
   *s = L'\0';
 
diff --git a/src/include/final/fstring.h b/src/include/final/fstring.h
index 26dbafcf..d3ecae45 100644
--- a/src/include/final/fstring.h
+++ b/src/include/final/fstring.h
@@ -287,7 +287,7 @@ class FString
 template <typename NumT
         , typename std::enable_if< std::is_integral<NumT>::value
                                 || std::is_floating_point<NumT>::value
-                                 , int>::type = 0 >
+                                 , int>::type >
 inline FString& FString::operator << (const NumT val)
 {
   FString numstr(FString().setNumber(val));