diff --git a/CHANGES.current b/CHANGES.current
index 5386a7d36..1e88a89d4 100644
--- a/CHANGES.current
+++ b/CHANGES.current
@@ -7,6 +7,18 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.0 (in progress)
 ===========================
 
+2020-09-25: wsfulton
+            [C#, Java] #1874 Add ability to change the modifiers for the interface
+            generated when using the %interface macros.
+
+            For C# use the 'csinterfacemodifiers' typemap.
+            For Java use the 'javainterfacemodifiers' typemap.
+
+            For example:
+
+              %typemap(csinterfacemodifiers) X "internal interface"
+
+
 2020-09-24: geefr
             [C#] #1868 Fix wchar_t* csvarout typemap for member variable wrappers.
 
diff --git a/Doc/Manual/CSharp.html b/Doc/Manual/CSharp.html
index ef4c0104d..fe8f7c4bd 100644
--- a/Doc/Manual/CSharp.html
+++ b/Doc/Manual/CSharp.html
@@ -240,6 +240,7 @@ javabody                    -> csbody
 javafinalize                -> csfinalize
 javadestruct                -> csdisposing and csdispose
 javadestruct_derived        -> csdisposing_derived and csdispose_derived
+javainterfacemodifiers      -> csinterfacemodifiers
 javainterfacecode           -> csinterfacecode
 </pre></div>
 
diff --git a/Doc/Manual/Java.html b/Doc/Manual/Java.html
index b9234b24f..2f55f5b04 100644
--- a/Doc/Manual/Java.html
+++ b/Doc/Manual/Java.html
@@ -6610,6 +6610,15 @@ Below shows an example modifying the finalizer, assuming the <tt>delete</tt> met
 
 </div>
 
+<p><tt>%typemap(javainterfacemodifiers)</tt></p>
+<div class="indent">
+Interface modifiers for the Java interface generated when using the <tt>interface</tt> feature, see <a href="Java.html#Java_interfaces">Java interfaces</a> section. The default is "public interface".
+<p>
+<b>Compatibility note:</b> This typemap was added in SWIG-4.1.0.
+</p>
+
+</div>
+
 <p><tt>%typemap(javainterfacecode, declaration="...", cptrmethod="...")</tt></p>
 <div class="indent">
 <p>
@@ -6709,7 +6718,7 @@ The "javaimports" typemap is ignored if the enum class is wrapped by an inner Ja
 <div class="code">
 <pre>
 [ javaimports typemap ]
-public interface [ javainterfacename ] {
+[ javainterfacemodifiers typemap ] [ javainterfacename ] {
 [ javainterfacecode:cptrmethod typemap attribute ]
 ... interface declarations ...
 }
diff --git a/Examples/test-suite/multiple_inheritance_interfaces.i b/Examples/test-suite/multiple_inheritance_interfaces.i
index 2972922fb..b7069647b 100644
--- a/Examples/test-suite/multiple_inheritance_interfaces.i
+++ b/Examples/test-suite/multiple_inheritance_interfaces.i
@@ -64,3 +64,31 @@ struct DerivedOverloaded : public BaseOverloaded {
   virtual void identical_overload(int i, const PTypedef &p = PTypedef()) {}
 };
 %}
+
+
+#if defined(SWIGJAVA) || defined(SWIGCSHARP)
+%interface(Space::X)
+#endif
+
+// Test the csinterfacemodifiers and javainterfacemodifiers typemaps.
+#if defined(SWIGCSHARP)
+/* change access from default "public class" to "internal class" */
+%typemap(csclassmodifiers) InternalAccess "internal class"
+/* The following modifiers are also needed with the above access modifier change */
+%typemap(csclassmodifiers) Space::X "internal class"
+%typemap(csinterfacemodifiers) Space::X "internal interface"
+#elif defined(SWIGJAVA)
+%typemap(javaclassmodifiers) InternalAccess "final /*notpublic*/ class"
+%typemap(javaclassmodifiers) Space::X "final class"
+%typemap(javainterfacemodifiers) Space::X "/*notpublic*/ interface"
+#endif
+
+%inline %{
+struct InternalAccess {};
+namespace Space {
+  class X {
+  public:
+    virtual void x(const InternalAccess& date) const = 0;
+  };
+}
+%}
diff --git a/Lib/csharp/csharp.swg b/Lib/csharp/csharp.swg
index ecc1983a7..0e180f576 100644
--- a/Lib/csharp/csharp.swg
+++ b/Lib/csharp/csharp.swg
@@ -894,6 +894,7 @@ SWIGINTERN const char * SWIG_UnpackData(const char *c, void *ptr, size_t sz) {
 %typemap(csinterfaces)                SWIGTYPE "global::System.IDisposable"
 %typemap(csinterfaces)                          SWIGTYPE *, SWIGTYPE &, SWIGTYPE &&, SWIGTYPE [], SWIGTYPE (CLASS::*) ""
 %typemap(csinterfaces_derived)        SWIGTYPE, SWIGTYPE *, SWIGTYPE &, SWIGTYPE &&, SWIGTYPE [], SWIGTYPE (CLASS::*) ""
+%typemap(csinterfacemodifiers)        SWIGTYPE, SWIGTYPE *, SWIGTYPE &, SWIGTYPE &&, SWIGTYPE [], SWIGTYPE (CLASS::*) "public interface"
 
 
 // csbody typemaps... these are in macros so that the visibility of the methods can be easily changed by users.
diff --git a/Lib/java/java.swg b/Lib/java/java.swg
index e9309331a..8f95f3a3b 100644
--- a/Lib/java/java.swg
+++ b/Lib/java/java.swg
@@ -1196,6 +1196,7 @@ Swig::LocalRefGuard $1_refguard(jenv, $input); }
 %typemap(javacode)             SWIGTYPE, SWIGTYPE *, SWIGTYPE &, SWIGTYPE &&, SWIGTYPE [], SWIGTYPE (CLASS::*) ""
 %typemap(javaimports)          SWIGTYPE, SWIGTYPE *, SWIGTYPE &, SWIGTYPE &&, SWIGTYPE [], SWIGTYPE (CLASS::*) ""
 %typemap(javainterfaces)       SWIGTYPE, SWIGTYPE *, SWIGTYPE &, SWIGTYPE &&, SWIGTYPE [], SWIGTYPE (CLASS::*) ""
+%typemap(javainterfacemodifiers) SWIGTYPE, SWIGTYPE *, SWIGTYPE &, SWIGTYPE &&, SWIGTYPE [], SWIGTYPE (CLASS::*) "public interface"
 
 /* javabody typemaps */
 
diff --git a/Source/Include/swigwarn.h b/Source/Include/swigwarn.h
index a08693ac8..8362cc08e 100644
--- a/Source/Include/swigwarn.h
+++ b/Source/Include/swigwarn.h
@@ -277,6 +277,7 @@
 #define WARN_JAVA_TYPEMAP_DIRECTORIN_NODESC   824
 #define WARN_JAVA_NO_DIRECTORCONNECT_ATTR     825
 #define WARN_JAVA_NSPACE_WITHOUT_PACKAGE      826
+#define WARN_JAVA_TYPEMAP_INTERFACEMODIFIERS_UNDEF 847
 
 /* please leave 810-829 free for Java */
 
@@ -297,6 +298,7 @@
 #define WARN_CSHARP_EXCODE                    844
 #define WARN_CSHARP_CANTHROW                  845
 #define WARN_CSHARP_NO_DIRECTORCONNECT_ATTR   846
+#define WARN_CSHARP_TYPEMAP_INTERFACEMODIFIERS_UNDEF 847
 
 /* please leave 830-849 free for C# */
 
diff --git a/Source/Modules/csharp.cxx b/Source/Modules/csharp.cxx
index 27cc65b32..5fef4caef 100644
--- a/Source/Modules/csharp.cxx
+++ b/Source/Modules/csharp.cxx
@@ -2050,7 +2050,8 @@ public:
 
   void emitInterfaceDeclaration(Node *n, String *interface_name, File *f_interface) {
     Printv(f_interface, typemapLookup(n, "csimports", Getattr(n, "classtypeobj"), WARN_NONE), "\n", NIL);
-    Printf(f_interface, "public interface %s", interface_name);
+    Printv(f_interface, typemapLookup(n, "csinterfacemodifiers", Getattr(n, "classtypeobj"), WARN_CSHARP_TYPEMAP_INTERFACEMODIFIERS_UNDEF), NIL);
+    Printf(f_interface, " %s", interface_name);
     if (List *baselist = Getattr(n, "bases")) {
       String *bases = 0;
       for (Iterator base = First(baselist); base.item; base = Next(base)) {
diff --git a/Source/Modules/java.cxx b/Source/Modules/java.cxx
index 231c6c0cb..7c8bed480 100644
--- a/Source/Modules/java.cxx
+++ b/Source/Modules/java.cxx
@@ -2145,7 +2145,8 @@ public:
     }
 
     Printv(f_interface, typemapLookup(n, "javaimports", Getattr(n, "classtypeobj"), WARN_NONE), "\n", NIL);
-    Printf(f_interface, "public interface %s", interface_name);
+    Printv(f_interface, typemapLookup(n, "javainterfacemodifiers", Getattr(n, "classtypeobj"), WARN_JAVA_TYPEMAP_INTERFACEMODIFIERS_UNDEF), NIL);
+    Printf(f_interface, " %s", interface_name);
     if (List *baselist = Getattr(n, "bases")) {
       String *bases = 0;
       for (Iterator base = First(baselist); base.item; base = Next(base)) {