diff --git a/quicktex/Decoder.h b/quicktex/Decoder.h
index 49168a6..258def4 100644
--- a/quicktex/Decoder.h
+++ b/quicktex/Decoder.h
@@ -31,7 +31,7 @@ template <class T> class Decoder {
     using Texture = T;
 
     virtual ~Decoder() = default;
-    virtual RawTexture Decode(const T &encoded) const;
+    virtual RawTexture Decode(const T &encoded) const = 0;
 };
 
 template <class T> class BlockDecoder : public Decoder<T> {
diff --git a/quicktex/Encoder.h b/quicktex/Encoder.h
index a232900..21db329 100644
--- a/quicktex/Encoder.h
+++ b/quicktex/Encoder.h
@@ -31,7 +31,7 @@ template <typename T> class Encoder {
     using Texture = T;
 
     virtual ~Encoder() = default;
-    virtual T Encode(const RawTexture &decoded) const;
+    virtual T Encode(const RawTexture &decoded) const = 0;
 };
 
 template <typename T> class BlockEncoder : public Encoder<T> {