diff --git a/flang/lib/Evaluate/intrinsics.cpp b/flang/lib/Evaluate/intrinsics.cpp
--- a/flang/lib/Evaluate/intrinsics.cpp
+++ b/flang/lib/Evaluate/intrinsics.cpp
@@ -10,6 +10,7 @@
 #include "flang/Common/Fortran.h"
 #include "flang/Common/enum-set.h"
 #include "flang/Common/idioms.h"
+#include "flang/Evaluate/check-expression.h"
 #include "flang/Evaluate/common.h"
 #include "flang/Evaluate/expression.h"
 #include "flang/Evaluate/fold.h"
@@ -82,6 +83,7 @@
     kindArg, // this argument is KIND=
     effectiveKind, // for function results: "kindArg" value, possibly defaulted
     dimArg, // this argument is DIM=
+    positiveInt, // integer arguments that must be positive
     likeMultiply, // for DOT_PRODUCT and MATMUL
     subscript, // address-sized integer
     size, // default KIND= for SIZE(), UBOUND, &c.
@@ -128,6 +130,7 @@
 static constexpr TypePattern AnyIntrinsic{IntrinsicType, KindCode::any};
 static constexpr TypePattern ExtensibleDerived{DerivedType, KindCode::any};
 static constexpr TypePattern AnyData{AnyType, KindCode::any};
+static constexpr TypePattern PositiveInt{IntType, KindCode::positiveInt};
 
 // Type is irrelevant, but not BOZ (for PRESENT(), OPTIONAL(), &c.)
 static constexpr TypePattern Addressable{AnyType, KindCode::addressable};
@@ -485,7 +488,7 @@
     {"ichar", {{"c", AnyChar}, DefaultingKIND}, KINDInt},
     {"ieor", {{"i", SameInt}, {"j", SameInt, Rank::elementalOrBOZ}}, SameInt},
     {"ieor", {{"i", BOZ}, {"j", SameInt}}, SameInt},
-    {"image_status", {{"image", SameInt}, OptionalTEAM}, DefaultInt},
+    {"image_status", {{"image", PositiveInt}, OptionalTEAM}, DefaultInt},
     {"index",
         {{"string", SameChar}, {"substring", SameChar},
             {"back", AnyLogical, Rank::elemental, Optionality::optional},
@@ -498,7 +501,7 @@
     {"ishft", {{"i", SameInt}, {"shift", AnyInt}}, SameInt},
     {"ishftc",
         {{"i", SameInt}, {"shift", AnyInt},
-            {"size", AnyInt, Rank::elemental, Optionality::optional}},
+            {"size", PositiveInt, Rank::elemental, Optionality::optional}},
         SameInt},
     {"isnan", {{"a", AnyFloating}}, DefaultLogical},
     {"is_contiguous", {{"array", Addressable, Rank::anyOrAssumedRank}},
@@ -1460,6 +1463,22 @@
                   "for intrinsic '%s'",
           d.keyword, name);
       break;
+    case KindCode::positiveInt:
+      CHECK(type->category() == TypeCategory::Integer);
+      if (const auto &expr{arg->UnwrapExpr()}) {
+        if (IsConstantExpr(*expr)) {
+          if (auto val{ToInt64(*expr)}) {
+            if (val <= 0) {
+              messages.Say(arg->sourceLocation(),
+                  "'%s=' argument for intrinsic '%s' must be a positive value"_err_en_US,
+                  d.keyword, name);
+              return std::nullopt;
+            }
+          }
+        }
+      }
+      argOk = true;
+      break;
     case KindCode::addressable:
     case KindCode::nullPointerType:
       argOk = true;
diff --git a/flang/test/Semantics/image_status.f90 b/flang/test/Semantics/image_status.f90
new file mode 100644
--- /dev/null
+++ b/flang/test/Semantics/image_status.f90
@@ -0,0 +1,95 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+! Check for semantic errors in image_status(), as defined in
+! section 16.9.98 of the Fortran 2018 standard
+
+program test_image_status
+  use iso_fortran_env, only : team_type, stat_failed_image, stat_stopped_image
+  implicit none
+
+  type(team_type) home, league(2)
+  integer n, image_num, array(5), coindexed[*], non_array_result, array_2d(10, 10), not_team_type
+  integer, parameter :: constant_integer = 2
+  integer, allocatable :: result_array(:), result_array_2d(:,:), wrong_rank_result(:)
+  logical wrong_arg_type_logical
+  real wrong_arg_type_real
+  character wrong_result_type
+
+  !___ standard-conforming statements ___
+  n = image_status(1)
+  n = image_status(constant_integer)
+  n = image_status(image_num)
+  n = image_status(array(1))
+  n = image_status(coindexed[1])
+  n = image_status(image=1)
+  result_array = image_status(array)
+  result_array_2d = image_status(array_2d)
+
+  n = image_status(2, home)
+  n = image_status(2, league(1))
+  n = image_status(image=2, team=home)
+  n = image_status(team=home, image=2)
+
+  if (image_status(1) .eq. stat_failed_image .or. image_status(1) .eq. stat_stopped_image) then
+     error stop
+  else if (image_status(1) .eq. 0) then
+     continue
+  end if
+
+  !___ non-conforming statements ___
+
+  !ERROR: 'image=' argument for intrinsic 'image_status' must be a positive value
+  n = image_status(-1)
+
+  !ERROR: 'image=' argument for intrinsic 'image_status' must be a positive value
+  n = image_status(0)
+
+  !ERROR: 'team=' argument has unacceptable rank 1
+  n = image_status(1, team=league)
+
+  !ERROR: Actual argument for 'image=' has bad type 'REAL(4)'
+  n = image_status(3.4)
+
+  !ERROR: Actual argument for 'image=' has bad type 'LOGICAL(4)'
+  n = image_status(wrong_arg_type_logical)
+
+  !ERROR: Actual argument for 'image=' has bad type 'REAL(4)'
+  n = image_status(wrong_arg_type_real)
+
+  !ERROR: Actual argument for 'team=' has bad type 'INTEGER(4)'
+  n = image_status(1, not_team_type)
+
+  !ERROR: Actual argument for 'team=' has bad type 'INTEGER(4)'
+  n = image_status(1, 1)
+
+  ! keyword argument with incorrect type
+  !ERROR: Actual argument for 'image=' has bad type 'REAL(4)'
+  n = image_status(image=3.4)
+
+  ! keyword argument with incorrect type
+  !ERROR: Actual argument for 'team=' has bad type 'INTEGER(4)'
+  n = image_status(1, team=1)
+
+  !ERROR: too many actual arguments for intrinsic 'image_status'
+  n = image_status(1, home, 2)
+
+  !ERROR: repeated keyword argument to intrinsic 'image_status'
+  n = image_status(image=1, image=2)
+
+  ! incorrect keyword argument name but valid type
+  !ERROR: unknown keyword argument to intrinsic 'image_status'
+  n = image_status(images=1)
+
+  ! incorrect keyword argument name but valid type
+  !ERROR: unknown keyword argument to intrinsic 'image_status'
+  n = image_status(1, my_team=home)
+
+  !ERROR: No intrinsic or user-defined ASSIGNMENT(=) matches scalar INTEGER(4) and rank 1 array of INTEGER(4)
+  non_array_result = image_status(image=array)
+
+  !ERROR: No intrinsic or user-defined ASSIGNMENT(=) matches rank 1 array of INTEGER(4) and rank 2 array of INTEGER(4)
+  wrong_rank_result = image_status(array_2d)
+
+  !ERROR: No intrinsic or user-defined ASSIGNMENT(=) matches operand types CHARACTER(KIND=1) and INTEGER(4)
+  wrong_result_type = image_status(1)
+
+end program test_image_status
diff --git a/flang/test/Semantics/ishftc.f90 b/flang/test/Semantics/ishftc.f90
new file mode 100644
--- /dev/null
+++ b/flang/test/Semantics/ishftc.f90
@@ -0,0 +1,15 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+! Check for semantic errors in ishftc() function calls
+
+program test_ishftc
+  implicit none
+
+  integer :: n
+
+  n = ishftc(3, 2, 3)
+  !ERROR: 'size=' argument for intrinsic 'ishftc' must be a positive value
+  n = ishftc(3, 2, -3)
+  !ERROR: 'size=' argument for intrinsic 'ishftc' must be a positive value
+  n = ishftc(3, 2, 0)
+
+end program test_ishftc