diff --git a/crypto/comp/comp.h b/crypto/comp/comp.h
index ab48b78ae97124b187d20104700914426fceedfd..5d59354a5715f9db49dcf258a59c39bd011b4456 100644
--- a/crypto/comp/comp.h
+++ b/crypto/comp/comp.h
@@ -8,19 +8,26 @@
 extern "C" {
 #endif
 
+typedef struct comp_ctx_st COMP_CTX;
+
 typedef struct comp_method_st
 	{
 	int type;		/* NID for compression library */
 	const char *name;	/* A text string to identify the library */
-	int (*init)();
-	void (*finish)();
-	int (*compress)();
-	int (*expand)();
-	long (*ctrl)();
-	long (*callback_ctrl)();
+	int (*init)(COMP_CTX *ctx);
+	void (*finish)(COMP_CTX *ctx);
+	int (*compress)(COMP_CTX *ctx,
+			unsigned char *out, unsigned int olen,
+			unsigned char *in, unsigned int ilen);
+	int (*expand)(COMP_CTX *ctx,
+		      unsigned char *out, unsigned int olen,
+		      unsigned char *in, unsigned int ilen);
+	/* The following two do NOTHING, but are kept for backward compatibility */
+	long (*ctrl)(void);
+	long (*callback_ctrl)(void);
 	} COMP_METHOD;
 
-typedef struct comp_ctx_st
+struct comp_ctx_st
 	{
 	COMP_METHOD *meth;
 	unsigned long compress_in;
@@ -29,7 +36,7 @@ typedef struct comp_ctx_st
 	unsigned long expand_out;
 
 	CRYPTO_EX_DATA	ex_data;
-	} COMP_CTX;
+	};
 
 
 COMP_CTX *COMP_CTX_new(COMP_METHOD *meth);