diff --git a/c/pgtypes.c b/c/pgtypes.c
index c51226b..cb4eb41 100644
--- a/c/pgtypes.c
+++ b/c/pgtypes.c
@@ -55,7 +55,7 @@ typedef struct {
     if (SvIOK(val)) iv = SvIV(val); \
     else if (SvNOK(val)) { \
         NV nv = SvNV(val); \
-        if (nv < IV_MIN || nv > IV_MAX || fabs(nv - floor(nv)) > 0.0000000001) SERR("expected integer");\
+        if (nv < IV_MIN || nv > IV_MAX || fabs((double)(nv - floor(nv))) > 0.0000000001) SERR("expected integer");\
         iv = SvIV(val); \
     } else if (SvPOK(val)) {\
         STRLEN sl; \
@@ -503,7 +503,7 @@ SENDFN(uuid) {
 RECVFN(timestamp) {
     RLEN(8);
     IV ts = fu_frombeI(64, buf);
-    return newSVnv(((double)ts / 1000000) + UNIX_PG_EPOCH);
+    return newSVnv(((NV)ts / 1000000) + UNIX_PG_EPOCH);
 }
 
 SENDFN(timestamp) {
diff --git a/t/json_format.t b/t/json_format.t
index e7f41d5..0797a4f 100644
--- a/t/json_format.t
+++ b/t/json_format.t
@@ -5,6 +5,7 @@ use Test::More;
 use Tie::Array;
 use Tie::Hash;
 use FU::Util 'json_format';
+use Config;
 
 
 sub MyToJSON::TO_JSON { [scalar @_, ref $_[0], ${$_[0]}] }
@@ -54,7 +55,7 @@ my @tests = (
     ''.$$, '"'.$$.'"',
     do { my $x = 12; utf8::decode($x); $x }, '"12"',
     do { no warnings 'numeric'; my $x = '19a'; $x += 0; $x }, '19',
-    1844674407370955161 / 10, '1.84467440737096e+17',
+    1844674407370955161 / 10, $Config{uselongdouble} ? 184467440737095516 : '1.84467440737096e+17',
 );
 
 my @errors = (
diff --git a/t/json_parse.t b/t/json_parse.t
index d223077..901d01f 100644
--- a/t/json_parse.t
+++ b/t/json_parse.t
@@ -3,6 +3,7 @@ use Test::More;
 use FU::Util 'json_parse';
 no warnings 'experimental::builtin';
 use builtin 'is_bool', 'created_as_number';
+use Config;
 
 my @error = (
     '',
@@ -96,8 +97,8 @@ num ' -0 ', 0;
 num '-9223372036854775808';
 num '9223372036854775807';
 num '18446744073709551615';
-num '-9223372036854775809', -9.22337203685478e+18;
-num '18446744073709551616', 1.84467440737096e+19;
+num '-9223372036854775809', $Config{uselongdouble} ? -9.22337203685477581e+18 : -9.22337203685478e+18;
+num '18446744073709551616', $Config{uselongdouble} ? 1.84467440737095516e+19 : 1.84467440737096e+19;
 num '1.234';
 num '1e5', 100000;
 num '1e+5', 100000;
diff --git a/t/pgtypes.t b/t/pgtypes.t
index 326ccce..ba18815 100644
--- a/t/pgtypes.t
+++ b/t/pgtypes.t
@@ -2,6 +2,7 @@ use v5.36;
 use Test::More;
 no warnings 'experimental::builtin';
 use builtin qw/true false is_bool created_as_number/;
+use Config;
 
 plan skip_all => $@ if !eval { require FU::Pg; } && $@ =~ /Unable to load libpq/;
 die $@ if $@;