diff --git a/flang/lib/Semantics/check-directive-structure.h b/flang/lib/Semantics/check-directive-structure.h
--- a/flang/lib/Semantics/check-directive-structure.h
+++ b/flang/lib/Semantics/check-directive-structure.h
@@ -168,8 +168,8 @@
   void RequiresConstantPositiveParameter(
       const C &clause, const parser::ScalarIntConstantExpr &i);
 
-  void RequiresPositiveParameter(
-      const C &clause, const parser::ScalarIntExpr &i);
+  void RequiresPositiveParameter(const C &clause,
+      const parser::ScalarIntExpr &i, parser::MessageFixedText msg = {"", 0});
 
   void OptionalConstantPositiveParameter(
       const C &clause, const std::optional<parser::ScalarIntConstantExpr> &o);
@@ -373,13 +373,18 @@
 template <typename D, typename C, typename PC, std::size_t ClauseEnumSize>
 void DirectiveStructureChecker<D, C, PC,
     ClauseEnumSize>::RequiresPositiveParameter(const C &clause,
-    const parser::ScalarIntExpr &i) {
+    const parser::ScalarIntExpr &i, parser::MessageFixedText msg) {
   if (const auto v{GetIntValue(i)}) {
     if (*v <= 0) {
-      context_.Say(GetContext().clauseSource,
-          "The parameter of the %s clause must be "
-          "a positive integer expression"_err_en_US,
-          parser::ToUpperCaseLetters(getClauseName(clause).str()));
+      if (msg.text().empty()) {
+        context_.Say(GetContext().clauseSource,
+            "The parameter of the %s clause must be "
+            "a positive integer expression"_err_en_US,
+            parser::ToUpperCaseLetters(getClauseName(clause).str()));
+      } else {
+        context_.Say(GetContext().clauseSource, std::move(msg),
+            parser::ToUpperCaseLetters(getClauseName(clause).str()));
+      }
     }
   }
 }
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -603,6 +603,12 @@
             parser::ToUpperCaseLetters(
                 parser::OmpScheduleClause::EnumToString(kind)));
       }
+      if (const auto &chunkExpr{
+              std::get<std::optional<parser::ScalarIntExpr>>(x.t)}) {
+        RequiresPositiveParameter(llvm::omp::Clause::OMPC_schedule, *chunkExpr,
+            "The chunk size of the schedule clause must be"
+            " a positive integer expression."_err_en_US);
+      }
     }
 
     if (ScheduleModifierHasType(
diff --git a/flang/test/Semantics/omp-do-schedule.f90 b/flang/test/Semantics/omp-do-schedule.f90
new file mode 100644
--- /dev/null
+++ b/flang/test/Semantics/omp-do-schedule.f90
@@ -0,0 +1,13 @@
+! RUN: %S/test_errors.sh %s %t %f18 -fopenmp
+! OpenMP Version 4.5
+! 2.7.1 Schedule Clause
+program omp_doSchedule
+  integer :: i,n
+  real ::  a(100), y(100), z(100)
+  !ERROR: The chunk size of the schedule clause must be a positive integer expression.
+  !$omp do schedule(static, -1)
+  do i=2,n+1
+    y(i) = z(i-1) + a(i)
+  end do
+  !$omp end do
+end program omp_doSchedule
diff --git a/flang/test/Semantics/omp-do-schedule02.f90 b/flang/test/Semantics/omp-do-schedule02.f90
new file mode 100644
--- /dev/null
+++ b/flang/test/Semantics/omp-do-schedule02.f90
@@ -0,0 +1,15 @@
+!RUN: %S/test_errors.sh %s %t %f18 -fopenmp
+! OpenMP Version 4.5
+! 2.7.1 Schedule Clause
+program omp_doSchedule
+  integer :: i,n
+  real ::  a(100), y(100), z(100)
+  integer,parameter :: b = 10
+  integer,parameter :: c = 11
+  !ERROR: The chunk size of the schedule clause must be a positive integer expression.
+  !$omp do schedule(static,b-c)
+  do i=2,n+1
+    y(i) = z(i-1) + a(i)
+  end do
+  !$omp end do
+end program omp_doSchedule
diff --git a/flang/test/Semantics/omp-do-schedule03.f90 b/flang/test/Semantics/omp-do-schedule03.f90
new file mode 100644
--- /dev/null
+++ b/flang/test/Semantics/omp-do-schedule03.f90
@@ -0,0 +1,28 @@
+! RUN: %S/test_symbols.sh %s %t %f18 -fopenmp
+! OpenMP Version 4.5
+! 2.7.1 Schedule Clause
+! Test that does not catch non constant integer expressions like xx - xx.
+  !DEF: /ompdoschedule MainProgram
+ program ompdoschedule
+  !DEF: /ompdoschedule/a ObjectEntity REAL(4)
+  !DEF: /ompdoschedule/y ObjectEntity REAL(4)
+  !DEF: /ompdoschedule/z ObjectEntity REAL(4)
+  real  a(100),y(100),z(100)
+  !DEF: /ompdoschedule/b ObjectEntity INTEGER(4)
+  !DEF: /ompdoschedule/i ObjectEntity INTEGER(4)
+  !DEF: /ompdoschedule/n ObjectEntity INTEGER(4)
+  integer  b,i,n
+  !REF: /ompdoschedule/b
+  b = 10
+!$omp do  schedule(static,b-b)
+ !DEF: /ompdoschedule/Block1/i (OmpPrivate, OmpPreDetermined) HostAssoc INTEGER(4)
+ !REF: /ompdoschedule/n
+  do i = 2,n+1
+  !REF: /ompdoschedule/y
+  !REF: /ompdoschedule/Block1/i
+  !REF: /ompdoschedule/z
+  !REF: /ompdoschedule/a
+    y(i) = z(i-1) + a(i)
+  end do
+ !$omp end do
+end program ompdoschedule
diff --git a/flang/test/Semantics/omp-do-schedule04.f90 b/flang/test/Semantics/omp-do-schedule04.f90
new file mode 100644
--- /dev/null
+++ b/flang/test/Semantics/omp-do-schedule04.f90
@@ -0,0 +1,32 @@
+! RUN: %S/test_symbols.sh %s %t %f18 -fopenmp
+! OpenMP Version 4.5
+! 2.7.1 Schedule Clause
+! Test that does not catch non constant integer expressions like xx - yy.
+
+  !DEF: /omp_doschedule (Subroutine) Subprogram
+subroutine omp_doschedule
+  implicit none
+  !DEF: /omp_doschedule/a ObjectEntity REAL(4)
+  !DEF: /omp_doschedule/y ObjectEntity REAL(4)
+  !DEF: /omp_doschedule/z ObjectEntity REAL(4)
+  real a(100),y(100),z(100)
+  !DEF: /omp_doschedule/i ObjectEntity INTEGER(4)
+  !DEF: /omp_doschedule/j ObjectEntity INTEGER(4)
+  !DEF: /omp_doschedule/k ObjectEntity INTEGER(4)
+  integer i,j,k
+
+  !REF: /omp_doschedule/j
+  j = 11
+  !REF: /omp_doschedule/k
+  k = 12
+!$omp do  schedule(static,j-k)
+ !DEF: /omp_doschedule/Block1/i (OmpPrivate,OmpPreDetermined) HostAssoc INTEGER(4)
+  do i = 1,10
+  !REF: /omp_doschedule/y
+  !REF: /omp_doschedule/Block1/i
+  !REF: /omp_doschedule/z
+  !REF: /omp_doschedule/a
+    y(i) = z(i-1)+a(i)
+  end do
+ !$omp end do
+end subroutine omp_doschedule