diff --git a/include/internal/catch_common.h b/include/internal/catch_common.h
index dfc0258b..53602ee6 100644
--- a/include/internal/catch_common.h
+++ b/include/internal/catch_common.h
@@ -24,8 +24,6 @@
 
 namespace Catch {
 
-    struct IConfig;
-
     struct CaseSensitive { enum Choice {
         Yes,
         No
diff --git a/include/internal/catch_context.h b/include/internal/catch_context.h
index 39307f59..5569eb71 100644
--- a/include/internal/catch_context.h
+++ b/include/internal/catch_context.h
@@ -12,8 +12,6 @@
 
 namespace Catch {
 
-    class TestCase;
-    class Stream;
     struct IResultCapture;
     struct IRunner;
     struct IConfig;
diff --git a/include/internal/catch_decomposer.h b/include/internal/catch_decomposer.h
index 5613e774..03c11568 100644
--- a/include/internal/catch_decomposer.h
+++ b/include/internal/catch_decomposer.h
@@ -50,8 +50,8 @@ namespace Catch {
         }
 
     public:
-        BinaryExpr( bool comparisionResult, LhsT lhs, StringRef op, RhsT rhs )
-        :   m_result( comparisionResult ),
+        BinaryExpr( bool comparisonResult, LhsT lhs, StringRef op, RhsT rhs )
+        :   m_result( comparisonResult ),
             m_lhs( lhs ),
             m_op( op ),
             m_rhs( rhs )
diff --git a/include/internal/catch_interfaces_capture.h b/include/internal/catch_interfaces_capture.h
index e8000154..d153a8bc 100644
--- a/include/internal/catch_interfaces_capture.h
+++ b/include/internal/catch_interfaces_capture.h
@@ -12,13 +12,11 @@
 
 namespace Catch {
 
-    class TestCase;
     class AssertionResult;
     struct AssertionInfo;
     struct SectionInfo;
     struct SectionEndInfo;
     struct MessageInfo;
-    class ScopedMessageBuilder;
     struct Counts;
     struct BenchmarkInfo;
     struct BenchmarkStats;
diff --git a/include/internal/catch_interfaces_reporter.h b/include/internal/catch_interfaces_reporter.h
index d1a5cb7c..be3044f9 100644
--- a/include/internal/catch_interfaces_reporter.h
+++ b/include/internal/catch_interfaces_reporter.h
@@ -165,7 +165,6 @@ namespace Catch {
         size_t iterations;
         uint64_t elapsedTimeInNanoseconds;
     };
-    class MultipleReporters;
 
     struct IStreamingReporter {
         virtual ~IStreamingReporter() = default;
diff --git a/include/internal/catch_interfaces_runner.h b/include/internal/catch_interfaces_runner.h
index 25decfb0..a0deaf7e 100644
--- a/include/internal/catch_interfaces_runner.h
+++ b/include/internal/catch_interfaces_runner.h
@@ -9,7 +9,6 @@
 #define TWOBLUECUBES_CATCH_INTERFACES_RUNNER_H_INCLUDED
 
 namespace Catch {
-    class TestCase;
 
     struct IRunner {
         virtual ~IRunner();