diff --git a/contrib/hstore/Makefile b/contrib/hstore/Makefile
index b29d02b137..61cc6d4ce3 100644
--- a/contrib/hstore/Makefile
+++ b/contrib/hstore/Makefile
@@ -15,7 +15,7 @@ PGFILEDESC = "hstore - key/value pair data type"
 
 HEADERS = hstore.h
 
-REGRESS = hstore
+REGRESS = hstore hstore_utf8
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
diff --git a/contrib/hstore/expected/hstore_utf8.out b/contrib/hstore/expected/hstore_utf8.out
new file mode 100644
index 0000000000..4405824413
--- /dev/null
+++ b/contrib/hstore/expected/hstore_utf8.out
@@ -0,0 +1,36 @@
+/*
+ * This test must be run in a database with UTF-8 encoding,
+ * because other encodings don't support all the characters used.
+ */
+SELECT getdatabaseencoding() <> 'UTF8'
+       AS skip_test \gset
+\if :skip_test
+\quit
+\endif
+SET client_encoding = utf8;
+-- UTF-8 locale bug on macOS: isspace(0x85) returns true.  \u0105 encodes
+-- as 0xc4 0x85 in UTF-8; the 0x85 was interpreted here as a whitespace.
+SELECT E'key\u0105=>value\u0105'::hstore;
+      hstore      
+------------------
+ "keyą"=>"valueą"
+(1 row)
+
+SELECT 'keyą=>valueą'::hstore;
+      hstore      
+------------------
+ "keyą"=>"valueą"
+(1 row)
+
+SELECT 'ą=>ą'::hstore;
+  hstore  
+----------
+ "ą"=>"ą"
+(1 row)
+
+SELECT 'keyąfoo=>valueą'::hstore;
+       hstore        
+---------------------
+ "keyąfoo"=>"valueą"
+(1 row)
+
diff --git a/contrib/hstore/expected/hstore_utf8_1.out b/contrib/hstore/expected/hstore_utf8_1.out
new file mode 100644
index 0000000000..37aead89c0
--- /dev/null
+++ b/contrib/hstore/expected/hstore_utf8_1.out
@@ -0,0 +1,8 @@
+/*
+ * This test must be run in a database with UTF-8 encoding,
+ * because other encodings don't support all the characters used.
+ */
+SELECT getdatabaseencoding() <> 'UTF8'
+       AS skip_test \gset
+\if :skip_test
+\quit
diff --git a/contrib/hstore/hstore_io.c b/contrib/hstore/hstore_io.c
index 745497c76f..47b0354d96 100644
--- a/contrib/hstore/hstore_io.c
+++ b/contrib/hstore/hstore_io.c
@@ -10,6 +10,7 @@
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "libpq/pqformat.h"
+#include "parser/scansup.h"
 #include "utils/builtins.h"
 #include "utils/json.h"
 #include "utils/jsonapi.h"
@@ -87,7 +88,7 @@ get_val(HSParser *state, bool ignoreeq, bool *escaped)
 			{
 				st = GV_WAITESCIN;
 			}
-			else if (!isspace((unsigned char) *(state->ptr)))
+			else if (!scanner_isspace((unsigned char) *(state->ptr)))
 			{
 				*(state->cur) = *(state->ptr);
 				state->cur++;
@@ -110,7 +111,7 @@ get_val(HSParser *state, bool ignoreeq, bool *escaped)
 				state->ptr--;
 				return true;
 			}
-			else if (isspace((unsigned char) *(state->ptr)))
+			else if (scanner_isspace((unsigned char) *(state->ptr)))
 			{
 				return true;
 			}
@@ -218,7 +219,7 @@ parse_hstore(HSParser *state)
 			{
 				elog(ERROR, "Unexpected end of string");
 			}
-			else if (!isspace((unsigned char) *(state->ptr)))
+			else if (!scanner_isspace((unsigned char) *(state->ptr)))
 			{
 				elog(ERROR, "Syntax error near '%c' at position %d", *(state->ptr), (int32) (state->ptr - state->begin));
 			}
@@ -266,7 +267,7 @@ parse_hstore(HSParser *state)
 			{
 				return;
 			}
-			else if (!isspace((unsigned char) *(state->ptr)))
+			else if (!scanner_isspace((unsigned char) *(state->ptr)))
 			{
 				elog(ERROR, "Syntax error near '%c' at position %d", *(state->ptr), (int32) (state->ptr - state->begin));
 			}
diff --git a/contrib/hstore/sql/hstore_utf8.sql b/contrib/hstore/sql/hstore_utf8.sql
new file mode 100644
index 0000000000..face878324
--- /dev/null
+++ b/contrib/hstore/sql/hstore_utf8.sql
@@ -0,0 +1,19 @@
+/*
+ * This test must be run in a database with UTF-8 encoding,
+ * because other encodings don't support all the characters used.
+ */
+
+SELECT getdatabaseencoding() <> 'UTF8'
+       AS skip_test \gset
+\if :skip_test
+\quit
+\endif
+
+SET client_encoding = utf8;
+
+-- UTF-8 locale bug on macOS: isspace(0x85) returns true.  \u0105 encodes
+-- as 0xc4 0x85 in UTF-8; the 0x85 was interpreted here as a whitespace.
+SELECT E'key\u0105=>value\u0105'::hstore;
+SELECT 'keyą=>valueą'::hstore;
+SELECT 'ą=>ą'::hstore;
+SELECT 'keyąfoo=>valueą'::hstore;