diff --git a/fcs/FSharp.Compiler.Service/FSharp.Compiler.Service.fsproj b/fcs/FSharp.Compiler.Service/FSharp.Compiler.Service.fsproj
index c5357aab06b..55a43730801 100644
--- a/fcs/FSharp.Compiler.Service/FSharp.Compiler.Service.fsproj
+++ b/fcs/FSharp.Compiler.Service/FSharp.Compiler.Service.fsproj
@@ -17,7 +17,7 @@
     <OtherFlags>$(OtherFlags) /warnon:1182</OtherFlags>
     <OtherFlags>$(OtherFlags) --times</OtherFlags>
     <NoWarn>$(NoWarn);44;62;69;65;54;61;75;62;9;2003;NU5125</NoWarn>
-    <Tailcalls>true</Tailcalls>
+    <Tailcalls>true</Tailcalls> <!-- .tail annotations always emitted for this binary, even in debug mode -->
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
   </PropertyGroup>
diff --git a/src/fsharp/FSharp.Compiler.Private/FSharp.Compiler.Private.fsproj b/src/fsharp/FSharp.Compiler.Private/FSharp.Compiler.Private.fsproj
index 46e8888f03b..2a38e3d10d1 100644
--- a/src/fsharp/FSharp.Compiler.Private/FSharp.Compiler.Private.fsproj
+++ b/src/fsharp/FSharp.Compiler.Private/FSharp.Compiler.Private.fsproj
@@ -13,6 +13,7 @@
     <OtherFlags>$(OtherFlags) --warnon:1182 --maxerrors:20 --extraoptimizationloops:1</OtherFlags>
     <UseFSharpProductVersion>true</UseFSharpProductVersion>
     <UseAssetTargetFallback>true</UseAssetTargetFallback>
+    <Tailcalls>true</Tailcalls> <!-- .tail annotations always emitted for this binary, even in debug mode -->
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(TargetFramework)' == 'net46' AND '$(OS)' == 'Windows_NT'">
diff --git a/src/fsharp/FSharp.Core/FSharp.Core.fsproj b/src/fsharp/FSharp.Core/FSharp.Core.fsproj
index ce9fa915f91..6ddda3f2e7e 100644
--- a/src/fsharp/FSharp.Core/FSharp.Core.fsproj
+++ b/src/fsharp/FSharp.Core/FSharp.Core.fsproj
@@ -14,6 +14,7 @@
     <DefineConstants>$(DefineConstants);FSHARP_CORE</DefineConstants>
     <DefineConstants Condition="'$(Configuration)' == 'Proto'">BUILDING_WITH_LKG;$(DefineConstants)</DefineConstants>
     <OtherFlags>$(OtherFlags) --warnon:1182 --compiling-fslib --compiling-fslib-40 --maxerrors:20 --extraoptimizationloops:1</OtherFlags>
+    <Tailcalls>true</Tailcalls> <!-- .tail annotations always emitted for this binary, even in debug mode -->
   </PropertyGroup>
 
   <ItemGroup>