diff --git a/include/gsl.h b/include/gsl.h
index ad064ba..b1f4086 100644
--- a/include/gsl.h
+++ b/include/gsl.h
@@ -101,7 +101,7 @@ public:
     not_null(std::nullptr_t) = delete;
     not_null(int) = delete;
     not_null<T>& operator=(std::nullptr_t) = delete;
-	not_null<T>& operator=(int) = delete;
+    not_null<T>& operator=(int) = delete;
     
     T get() const {
 #ifdef _MSC_VER
@@ -113,8 +113,8 @@ public:
     operator T() const {  return get(); }
     T operator->() const { return get(); }
 
-	bool operator==(const T& rhs) const { return ptr_ == rhs; }
-	bool operator!=(const T& rhs) const { return !(*this == rhs); }
+    bool operator==(const T& rhs) const { return ptr_ == rhs; }
+    bool operator!=(const T& rhs) const { return !(*this == rhs); }
 private:
     T ptr_;
 
diff --git a/include/gsl_assert.h b/include/gsl_assert.h
index 51e8ab6..4bee885 100644
--- a/include/gsl_assert.h
+++ b/include/gsl_assert.h
@@ -47,7 +47,7 @@ namespace gsl
 {
 struct fail_fast : public std::runtime_error 
 {
-	explicit fail_fast(char const* const message) : std::runtime_error(message) {}   
+    explicit fail_fast(char const* const message) : std::runtime_error(message) {}
 };
 }
 
diff --git a/include/string_span.h b/include/string_span.h
index fdcbf31..1126f24 100644
--- a/include/string_span.h
+++ b/include/string_span.h
@@ -255,7 +255,7 @@ public:
     constexpr basic_string_span(basic_string_span&& other) = default;
 #else
     constexpr basic_string_span(basic_string_span&& other)
-    	: span_(std::move(other.span_))
+        : span_(std::move(other.span_))
     {}
 #endif