diff --git a/lib/common/debug.c b/lib/common/debug.c
index aa2063f32..64f0b712b 100644
--- a/lib/common/debug.c
+++ b/lib/common/debug.c
@@ -1,4 +1,3 @@
 #include "debug.h"
 
 /* Implementation moved to Rust (rust/src/debug.rs) */
-extern int g_debuglevel;
diff --git a/lib/common/error_private.c b/lib/common/error_private.c
index ea09f74b0..80b4e5d55 100644
--- a/lib/common/error_private.c
+++ b/lib/common/error_private.c
@@ -1,4 +1,3 @@
 #include "error_private.h"
 
-// Implementation moved to Rust
-extern const char* ERR_getErrorString(ERR_enum code);
+/* Implementation moved to Rust (rust/src/errors.rs). */
diff --git a/lib/common/zstd_common.c b/lib/common/zstd_common.c
index 9d234b750..1ddce2f76 100644
--- a/lib/common/zstd_common.c
+++ b/lib/common/zstd_common.c
@@ -2,9 +2,3 @@
 #include "zstd_internal.h"
 
 /* Implementation moved to Rust (rust/src/zstd_common.rs) */
-extern unsigned ZSTD_versionNumber(void);
-extern const char* ZSTD_versionString(void);
-extern unsigned ZSTD_isError(size_t code);
-extern const char* ZSTD_getErrorName(size_t code);
-extern ZSTD_ErrorCode ZSTD_getErrorCode(size_t code);
-extern const char* ZSTD_getErrorString(ZSTD_ErrorCode code);