diff --git a/doc/man3/flux_event_decode.rst b/doc/man3/flux_event_decode.rst
index 09cb24aed25c..591ce35de57c 100644
--- a/doc/man3/flux_event_decode.rst
+++ b/doc/man3/flux_event_decode.rst
@@ -18,7 +18,7 @@ SYNOPSIS
    int flux_event_decode_raw (const flux_msg_t *msg,
                               const char **topic,
                               const void **data,
-                              int *len);
+                              size_t *len);
 
    int flux_event_unpack (const flux_msg_t *msg,
                           const char **topic,
@@ -29,7 +29,7 @@ SYNOPSIS
 
    flux_msg_t *flux_event_encode_raw (const char *topic,
                                       const void *data,
-                                      int len);
+                                      size_t len);
 
    flux_msg_t *flux_event_pack (const char *topic,
                                 const char *fmt,
diff --git a/doc/man3/flux_event_publish.rst b/doc/man3/flux_event_publish.rst
index 7869d9e5623e..239f81cd1be9 100644
--- a/doc/man3/flux_event_publish.rst
+++ b/doc/man3/flux_event_publish.rst
@@ -26,7 +26,7 @@ SYNOPSIS
                                           const char *topic,
                                           int flags,
                                           const void *data,
-                                          int len);
+                                          size_t len);
 
    int flux_event_publish_get_seq (flux_future_t *f, int *seq);
 
diff --git a/doc/man3/flux_kvs_lookup.rst b/doc/man3/flux_kvs_lookup.rst
index 04b81f2d4ce4..f85130694268 100644
--- a/doc/man3/flux_kvs_lookup.rst
+++ b/doc/man3/flux_kvs_lookup.rst
@@ -29,7 +29,7 @@ SYNOPSIS
 
    int flux_kvs_lookup_get_raw (flux_future_t *f,
                                 const void **data
-                                int *len);
+                                size_t *len);
 
    int flux_kvs_lookup_get_dir (flux_future_t *f,
                                 const flux_kvsdir_t **dir);
diff --git a/doc/man3/flux_kvs_txn_create.rst b/doc/man3/flux_kvs_txn_create.rst
index cb7531f66410..b83f08dc5a79 100644
--- a/doc/man3/flux_kvs_txn_create.rst
+++ b/doc/man3/flux_kvs_txn_create.rst
@@ -50,7 +50,7 @@ SYNOPSIS
                              int flags,
                              const char *key,
                              const void *data,
-                             int len);
+                             size_t len);
 
    int flux_kvs_txn_put_treeobj (flux_kvs_txn_t *txn,
                                  int flags,
diff --git a/doc/man3/flux_request_decode.rst b/doc/man3/flux_request_decode.rst
index baf0f650a3e0..1a4befb94244 100644
--- a/doc/man3/flux_request_decode.rst
+++ b/doc/man3/flux_request_decode.rst
@@ -23,7 +23,7 @@ SYNOPSIS
    int flux_request_decode_raw (const flux_msg_t *msg,
                                 const char **topic,
                                 const void **data,
-                                int *len);
+                                size_t *len);
 
 Link with :command:`-lflux-core`.
 
diff --git a/doc/man3/flux_request_encode.rst b/doc/man3/flux_request_encode.rst
index a92ce790ce92..7f2c7fc25124 100644
--- a/doc/man3/flux_request_encode.rst
+++ b/doc/man3/flux_request_encode.rst
@@ -15,7 +15,7 @@ SYNOPSIS
 
    flux_msg_t *flux_request_encode_raw (const char *topic,
                                         void *data,
-                                        int len);
+                                        size_t len);
 
 Link with :command:`-lflux-core`.
 
diff --git a/doc/man3/flux_respond.rst b/doc/man3/flux_respond.rst
index 757380e60b33..18aadedc8f7f 100644
--- a/doc/man3/flux_respond.rst
+++ b/doc/man3/flux_respond.rst
@@ -23,7 +23,7 @@ SYNOPSIS
    int flux_respond_raw (flux_t *h,
                          const flux_msg_t *request,
                          const void *data,
-                         int length);
+                         size_t length);
 
    int flux_respond_error (flux_t *h,
                            const flux_msg_t *request,
diff --git a/doc/man3/flux_response_decode.rst b/doc/man3/flux_response_decode.rst
index 31aea149926f..11b5d877d1ea 100644
--- a/doc/man3/flux_response_decode.rst
+++ b/doc/man3/flux_response_decode.rst
@@ -18,7 +18,7 @@ SYNOPSIS
    int flux_response_decode_raw (const flux_msg_t *msg,
                                  const char **topic,
                                  const void **data,
-                                 int *len);
+                                 size_t *len);
 
    int flux_response_decode_error (const flux_msg_t *msg,
                                    const char *errstr);
diff --git a/doc/man3/flux_rpc.rst b/doc/man3/flux_rpc.rst
index f754fa57f1ea..76a43b97830d 100644
--- a/doc/man3/flux_rpc.rst
+++ b/doc/man3/flux_rpc.rst
@@ -27,7 +27,7 @@ SYNOPSIS
    flux_future_t *flux_rpc_raw (flux_t *h,
                                 const char *topic,
                                 const void *data,
-                                int len,
+                                size_t len,
                                 uint32_t nodeid,
                                 int flags);
 
@@ -42,7 +42,7 @@ SYNOPSIS
 
    int flux_rpc_get_raw (flux_future_t *f,
                          const void **data,
-                         int *len);
+                         size_t *len);
 
    uint32_t flux_rpc_get_matchtag (flux_future_t *f);