diff --git a/library/pkparse.c b/library/pkparse.c
index edf6e31..8e1aa6e 100644
--- a/library/pkparse.c
+++ b/library/pkparse.c
@@ -1072,7 +1072,7 @@
 
 #if defined(MBEDTLS_RSA_C)
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( key[keylen - 1] != '\0' )
+    if( keylen == 0 || key[keylen - 1] != '\0' )
         ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
     else
         ret = mbedtls_pem_read_buffer( &pem,
@@ -1105,7 +1105,7 @@
 
 #if defined(MBEDTLS_ECP_C)
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( key[keylen - 1] != '\0' )
+    if( keylen == 0 || key[keylen - 1] != '\0' )
         ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
     else
         ret = mbedtls_pem_read_buffer( &pem,
@@ -1136,7 +1136,7 @@
 #endif /* MBEDTLS_ECP_C */
 
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( key[keylen - 1] != '\0' )
+    if( keylen == 0 || key[keylen - 1] != '\0' )
         ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
     else
         ret = mbedtls_pem_read_buffer( &pem,
@@ -1159,7 +1159,7 @@
 
 #if defined(MBEDTLS_PKCS12_C) || defined(MBEDTLS_PKCS5_C)
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( key[keylen - 1] != '\0' )
+    if( keylen == 0 || key[keylen - 1] != '\0' )
         ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
     else
         ret = mbedtls_pem_read_buffer( &pem,
@@ -1257,7 +1257,7 @@
     mbedtls_pem_init( &pem );
 
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( key[keylen - 1] != '\0' )
+    if( keylen == 0 || key[keylen - 1] != '\0' )
         ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
     else
         ret = mbedtls_pem_read_buffer( &pem,