diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index ef45fbf1fc..e23e91d9bb 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -124,7 +124,10 @@ PGconn *PQconnectdbParams(const char * const *keywords,
       <para>
        When <literal>expand_dbname</literal> is non-zero, the
        <parameter>dbname</parameter> key word value is allowed to be recognized
-       as a connection string. More details on the possible formats appear in
+       as a connection string. Only the first occurrence of
+       <parameter>dbname</parameter> is expanded this way, any subsequent
+       <parameter>dbname</parameter> value is processed as plain database name. More
+       details on the possible connection string formats appear in
        <xref linkend="libpq-connstring">.
       </para>
 
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 6663c48352..703cbac37a 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -4379,10 +4379,11 @@ conninfo_parse(const char *conninfo, PQExpBuffer errorMessage,
  * Defaults are supplied (from a service file, environment variables, etc)
  * for unspecified options, but only if use_defaults is TRUE.
  *
- * If expand_dbname is non-zero, and the value passed for keyword "dbname" is a
- * connection string (as indicated by recognized_connection_string) then parse
- * and process it, overriding any previously processed conflicting
- * keywords. Subsequent keywords will take precedence, however.
+ * If expand_dbname is non-zero, and the value passed for the first occurrence
+ * of "dbname" keyword is a connection string (as indicated by
+ * recognized_connection_string) then parse and process it, overriding any
+ * previously processed conflicting keywords. Subsequent keywords will take
+ * precedence, however.
  */
 static PQconninfoOption *
 conninfo_array_parse(const char *const * keywords, const char *const * values,
@@ -4458,7 +4459,7 @@ conninfo_array_parse(const char *const * keywords, const char *const * values,
 			}
 
 			/*
-			 * If we are on the dbname parameter, and we have a parsed
+			 * If we are on the first dbname parameter, and we have a parsed
 			 * connection string, copy those parameters across, overriding any
 			 * existing previous settings.
 			 */
@@ -4492,6 +4493,12 @@ conninfo_array_parse(const char *const * keywords, const char *const * values,
 						}
 					}
 				}
+				/*
+				 * Forget the parsed connection string, so that any subsequent
+				 * dbname parameters will not be expanded.
+				 */
+				PQconninfoFree(dbname_options);
+				dbname_options = NULL;
 			}
 			else
 			{