diff --git a/lib/mime.c b/lib/mime.c
index 759ade085..11d387d62 100644
--- a/lib/mime.c
+++ b/lib/mime.c
@@ -282,7 +282,7 @@ static size_t mime_mem_read(char *buffer, size_t size, size_t nitems,
                             void *instream)
 {
   struct Curl_mimepart *part = (struct Curl_mimepart *) instream;
-  size_t sz = part->datasize - part->state.offset;
+  size_t sz = (size_t) part->datasize - part->state.offset;
 
   (void) size;   /* Always 1.*/
 
@@ -312,7 +312,7 @@ static int mime_mem_seek(void *instream, curl_off_t offset, int whence)
   if(offset < 0 || offset > part->datasize)
     return CURL_SEEKFUNC_FAIL;
 
-  part->state.offset = offset;
+  part->state.offset = (size_t) offset;
   return CURL_SEEKFUNC_OK;
 }
 
diff --git a/src/tool_setopt.c b/src/tool_setopt.c
index 6cb6bb3e3..4e25e9e12 100644
--- a/src/tool_setopt.c
+++ b/src/tool_setopt.c
@@ -210,14 +210,18 @@ static const NameValue setopt_nv_CURLNONZERODEFAULTS[] = {
 
 /* Escape string to C string syntax.  Return NULL if out of memory.
  * Is this correct for those wacky EBCDIC guys? */
-static char *c_escape(const char *str, ssize_t len)
+static char *c_escape(const char *str, ssize_t plen)
 {
   const char *s;
   unsigned char c;
   char *escaped, *e;
+  size_t len = plen == -1? strlen(str): (size_t) plen;
+
+  /* Check for possible overflow. */
+  if(len > (~(size_t) 0) / 4)
+    return NULL;
+
   /* Allocate space based on worst-case */
-  if(len < 0)
-    len = strlen(str);
   escaped = malloc(4 * len + 1);
   if(!escaped)
     return NULL;
@@ -474,7 +478,7 @@ static CURLcode libcurl_generate_mime(curl_mime *mime, int *mimeno)
           ;
         size = (cp == data + part->datasize)? (curl_off_t) -1: part->datasize;
         Curl_safefree(escaped);
-        escaped = c_escape(data, part->datasize);
+        escaped = c_escape(data, (ssize_t) part->datasize);
         if(data != part->data)
           Curl_safefree(data);
         if(!escaped)