diff --git a/cmake/macro-conf/support/platform/linux/base.cmakedef b/cmake/macro-conf/support/platform/linux/base.cmakedef
index 152f7629fe..162a67c545 100644
--- a/cmake/macro-conf/support/platform/linux/base.cmakedef
+++ b/cmake/macro-conf/support/platform/linux/base.cmakedef
@@ -42,9 +42,6 @@ LONG_LONG_ALLOWED=1
 INTEGER_VALUE_REPR_IS_A_HOST_INTEGER=0
 TYPE_FOR_AN_INTEGER_VALUE=unsigned long long
 TYPE_FOR_A_SIGNED_INTEGER_VALUE=long long
-MAX_INTEGER_VALUE=9223372036854775807LL
-MIN_INTEGER_VALUE=(-MAX_INTEGER_VALUE-1)
-MAX_UNSIGNED_INTEGER_VALUE=18446744073709551615ULL
 FP_LONG_DOUBLE_IS_80BIT_EXTENDED=1
 LINKER_CAN_DISCARD_DUPLICATE_DEFINITIONS=1
 
diff --git a/src/Changes b/src/Changes
index de5c529b76..cf653668fe 100644
--- a/src/Changes
+++ b/src/Changes
@@ -1,5 +1,23 @@
 Version 7.1
 
+10/11/26  [GH #38]
+Integer value limits for a 128-bit host integer representation
+
+When target integers are represented by a 128-bit host integer (for example,
+in the macOS CMake configurations), MAX_INTEGER_VALUE, MIN_INTEGER_VALUE, and
+MAX_UNSIGNED_INTEGER_VALUE still defaulted to 64-bit limits.  As a result,
+constant arithmetic on __int128 values that did not fit in 64 bits could be
+wrongly diagnosed as overflowing.  For example:
+
+  constexpr __int128 s = (__int128)1 << 100;
+  static_assert(s * 4 == ((__int128)1 << 102), "");  // Previously an error.
+
+This is now fixed: When __int128 extensions are allowed, the default limits
+are those of the 128-bit types.  The Linux configurations no longer hard-code
+the 64-bit limits, so they also get the 128-bit limits when the integer value
+types are changed to the 128-bit types.
+
+
 10/9/26  [GH #27]
 Clearer diagnostic when auto is deduced from an incomplete type
 
diff --git a/src/defines_linux.h b/src/defines_linux.h
index 47fa8d5264..0e6b9ca149 100644
--- a/src/defines_linux.h
+++ b/src/defines_linux.h
@@ -282,9 +282,6 @@ Linux.
 #ifndef TYPE_FOR_A_SIGNED_INTEGER_VALUE
 #define TYPE_FOR_A_SIGNED_INTEGER_VALUE long long
 #endif /* TYPE_FOR_A_SIGNED_INTEGER_VALUE */
-#define MAX_INTEGER_VALUE 9223372036854775807LL
-#define MIN_INTEGER_VALUE (-MAX_INTEGER_VALUE-1)
-#define MAX_UNSIGNED_INTEGER_VALUE 18446744073709551615ULL
 
 #if defined(__aarch64__) || defined(__riscv)
 /* 64-bit ARM and RISC-V use a 128-bit long double representation. */
diff --git a/src/targ_def.h b/src/targ_def.h
index 50edb81f9e..49d7b7132f 100644
--- a/src/targ_def.h
+++ b/src/targ_def.h
@@ -1536,6 +1536,9 @@ typedef TYPE_FOR_A_SIGNED_INTEGER_VALUE a_signed_integer_value;
 
 /* Minimum and maximum values that can be represented in an_integer_value. */
 #ifndef MAX_INTEGER_VALUE
+#if INT128_EXTENSIONS_ALLOWED
+#define MAX_INTEGER_VALUE ((__int128_t)(~(__uint128_t)0 >> 1))
+#else /* !INT128_EXTENSIONS_ALLOWED */
 #if LONG_LONG_ALLOWED
 #ifdef LLONG_MAX
 #define MAX_INTEGER_VALUE LLONG_MAX
@@ -1545,8 +1548,12 @@ typedef TYPE_FOR_A_SIGNED_INTEGER_VALUE a_signed_integer_value;
 #else /* !LONG_LONG_ALLOWED */
 #define MAX_INTEGER_VALUE LONG_MAX
 #endif /* LONG_LONG_ALLOWED */
+#endif /* INT128_EXTENSIONS_ALLOWED */
 #endif /* ifndef MAX_INTEGER_VALUE */
 #ifndef MIN_INTEGER_VALUE
+#if INT128_EXTENSIONS_ALLOWED
+#define MIN_INTEGER_VALUE (-MAX_INTEGER_VALUE-1)
+#else /* !INT128_EXTENSIONS_ALLOWED */
 #if LONG_LONG_ALLOWED
 #if defined(LLONG_MIN) && LLONG_MIN < LLONG_MAX /*lint !e30*/
 /* The preceding condition detects an incorrect definition of LLONG_MIN
@@ -1558,8 +1565,12 @@ typedef TYPE_FOR_A_SIGNED_INTEGER_VALUE a_signed_integer_value;
 #else /* !LONG_LONG_ALLOWED */
 #define MIN_INTEGER_VALUE LONG_MIN
 #endif /* LONG_LONG_ALLOWED */
+#endif /* INT128_EXTENSIONS_ALLOWED */
 #endif /* ifndef MIN_INTEGER_VALUE */
 #ifndef MAX_UNSIGNED_INTEGER_VALUE
+#if INT128_EXTENSIONS_ALLOWED
+#define MAX_UNSIGNED_INTEGER_VALUE (~(__uint128_t)0)
+#else /* !INT128_EXTENSIONS_ALLOWED */
 #if LONG_LONG_ALLOWED
 #ifdef ULLONG_MAX
 #define MAX_UNSIGNED_INTEGER_VALUE ULLONG_MAX
@@ -1569,6 +1580,7 @@ typedef TYPE_FOR_A_SIGNED_INTEGER_VALUE a_signed_integer_value;
 #else /* !LONG_LONG_ALLOWED */
 #define MAX_UNSIGNED_INTEGER_VALUE ULONG_MAX
 #endif /* LONG_LONG_ALLOWED */
+#endif /* INT128_EXTENSIONS_ALLOWED */
 #endif /* ifndef MAX_UNSIGNED_INTEGER_VALUE */
 #ifndef BITS_IN_AN_INTEGER_VALUE
 #define BITS_IN_AN_INTEGER_VALUE (sizeof(an_integer_value) * CHAR_BIT)