diff --git a/src/ffi/c.rs b/src/ffi/c.rs
index 48acd438..32864f8f 100644
--- a/src/ffi/c.rs
+++ b/src/ffi/c.rs
@@ -226,6 +226,12 @@ impl InflateBackend for Inflate {
         self.inner.total_in += (raw.next_in as usize - input.as_ptr() as usize) as u64;
         self.inner.total_out += (raw.next_out as usize - output.as_ptr() as usize) as u64;
 
+        // reset these pointers so we don't accidentally read them later
+        raw.next_in = ptr::null_mut();
+        raw.avail_in = 0;
+        raw.next_out = ptr::null_mut();
+        raw.avail_out = 0;
+
         match rc {
             MZ_DATA_ERROR | MZ_STREAM_ERROR => mem::decompress_failed(self.inner.msg()),
             MZ_OK => Ok(Status::Ok),
@@ -314,6 +320,12 @@ impl DeflateBackend for Deflate {
         self.inner.total_in += (raw.next_in as usize - input.as_ptr() as usize) as u64;
         self.inner.total_out += (raw.next_out as usize - output.as_ptr() as usize) as u64;
 
+        // reset these pointers so we don't accidentally read them later
+        raw.next_in = ptr::null_mut();
+        raw.avail_in = 0;
+        raw.next_out = ptr::null_mut();
+        raw.avail_out = 0;
+
         match rc {
             MZ_OK => Ok(Status::Ok),
             MZ_BUF_ERROR => Ok(Status::BufError),