diff --git a/intl/Encoding.h b/intl/Encoding.h
index e478a9b752a3..56f25bcf854a 100644
--- a/intl/Encoding.h
+++ b/intl/Encoding.h
@@ -645,10 +645,7 @@ class Encoding final {
    * BOM sniffing may cause the returned decoder to morph into a decoder
    * for UTF-8, UTF-16LE or UTF-16BE instead of this encoding.
    */
-  inline UniquePtr<Decoder> NewDecoder() const {
-    UniquePtr<Decoder> decoder(encoding_new_decoder(this));
-    return decoder;
-  }
+  UniquePtr<Decoder> NewDecoder() const;
 
   /**
    * Instantiates a new decoder for this encoding with BOM sniffing enabled
@@ -670,10 +667,7 @@ class Encoding final {
    * (potentially malformed) input to the decoding algorithm for this
    * encoding.
    */
-  inline UniquePtr<Decoder> NewDecoderWithBOMRemoval() const {
-    UniquePtr<Decoder> decoder(encoding_new_decoder_with_bom_removal(this));
-    return decoder;
-  }
+  UniquePtr<Decoder> NewDecoderWithBOMRemoval() const;
 
   /**
    * Instantiates a new decoder for this encoding with BOM removal
@@ -700,10 +694,7 @@ class Encoding final {
    * removed the BOM, the caller should use `NewDecoderWithBOMRemoval()`
    * instead of this method to cause the BOM to be removed.
    */
-  inline UniquePtr<Decoder> NewDecoderWithoutBOMHandling() const {
-    UniquePtr<Decoder> decoder(encoding_new_decoder_without_bom_handling(this));
-    return decoder;
-  }
+  UniquePtr<Decoder> NewDecoderWithoutBOMHandling() const;
 
   /**
    * Instantiates a new decoder for this encoding with BOM handling disabled
@@ -724,10 +715,7 @@ class Encoding final {
   /**
    * Instantiates a new encoder for the output encoding of this encoding.
    */
-  inline UniquePtr<Encoder> NewEncoder() const {
-    UniquePtr<Encoder> encoder(encoding_new_encoder(this));
-    return encoder;
-  }
+  UniquePtr<Encoder> NewEncoder() const;
 
   /**
    * Instantiates a new encoder for the output encoding of this encoding
@@ -1345,6 +1333,26 @@ class Encoder final {
   Encoder& operator=(const Encoder&) = delete;
 };
 
+inline UniquePtr<Decoder> Encoding::NewDecoder() const {
+  UniquePtr<Decoder> decoder(encoding_new_decoder(this));
+  return decoder;
+}
+
+inline UniquePtr<Decoder> Encoding::NewDecoderWithBOMRemoval() const {
+  UniquePtr<Decoder> decoder(encoding_new_decoder_with_bom_removal(this));
+  return decoder;
+}
+
+inline UniquePtr<Decoder> Encoding::NewDecoderWithoutBOMHandling() const {
+  UniquePtr<Decoder> decoder(encoding_new_decoder_without_bom_handling(this));
+  return decoder;
+}
+
+inline UniquePtr<Encoder> Encoding::NewEncoder() const {
+  UniquePtr<Encoder> encoder(encoding_new_encoder(this));
+  return encoder;
+}
+
 };  // namespace mozilla
 
 #endif  // mozilla_Encoding_h