diff --git a/README.md b/README.md
index 13fa7cb..9b2a1a0 100644
--- a/README.md
+++ b/README.md
@@ -106,7 +106,7 @@ If your input is formatted as newline-delimited GeoJSON, use `-P` to make input
 
 ### Projection of input
 
- * `-s` _projection_ or `--projection=`_projection_: Specify the projection of the input data. Currently supported are `EPSG:4326` (WGS84, the default) and `EPSG:3857` (Web Mercator).
+ * `-s` _projection_ or `--projection=`_projection_: Specify the projection of the input data. Currently supported are `EPSG:4326` (WGS84, the default) and `EPSG:3857` (Web Mercator). In general you should use WGS84 for your input files if at all possible.
 
 ### Zoom levels
 
diff --git a/geojson.cpp b/geojson.cpp
index cb40ae4..b162236 100644
--- a/geojson.cpp
+++ b/geojson.cpp
@@ -567,7 +567,8 @@ void check_crs(json_object *j, const char *reading) {
 			json_object *name = json_hash_get(properties, "name");
 			if (name->type == JSON_STRING) {
 				if (strcmp(name->string, projection->alias) != 0) {
-					fprintf(stderr, "%s: Warning: GeoJSON specified projection \"%s\", not \"%s\".\n", reading, name->string, projection->alias);
+					fprintf(stderr, "%s: Warning: GeoJSON specified projection \"%s\", not the expected \"%s\".\n", reading, name->string, projection->alias);
+					fprintf(stderr, "%s: If \"%s\" is not the expected projection, use -s to specify the right one.\n", reading, projection->alias);
 				}
 			}
 		}
diff --git a/man/tippecanoe.1 b/man/tippecanoe.1
index 9d38836..6712f67 100644
--- a/man/tippecanoe.1
+++ b/man/tippecanoe.1
@@ -112,7 +112,7 @@ rather than a stream that can only be read sequentially.
 .SS Projection of input
 .RS
 .IP \(bu 2
-\fB\fC\-s\fR \fIprojection\fP or \fB\fC\-\-projection=\fR\fIprojection\fP: Specify the projection of the input data. Currently supported are \fB\fCEPSG:4326\fR (WGS84, the default) and \fB\fCEPSG:3857\fR (Web Mercator).
+\fB\fC\-s\fR \fIprojection\fP or \fB\fC\-\-projection=\fR\fIprojection\fP: Specify the projection of the input data. Currently supported are \fB\fCEPSG:4326\fR (WGS84, the default) and \fB\fCEPSG:3857\fR (Web Mercator). In general you should use WGS84 for your input files if at all possible.
 .RE
 .SS Zoom levels
 .RS