diff --git a/csharp/ql/lib/semmle/code/csharp/Callable.qll b/csharp/ql/lib/semmle/code/csharp/Callable.qll
index 03de29d6d431..6384f4582769 100644
--- a/csharp/ql/lib/semmle/code/csharp/Callable.qll
+++ b/csharp/ql/lib/semmle/code/csharp/Callable.qll
@@ -8,6 +8,7 @@ import Stmt
 import Type
 import exprs.Call
 private import commons.QualifiedName
+private import commons.Collections
 private import semmle.code.csharp.ExprOrStmtParent
 private import semmle.code.csharp.metrics.Complexity
 private import TypeRef
@@ -273,7 +274,7 @@ class Method extends Callable, Virtualizable, Attributable, @method {
   Type getParamsType() {
     exists(Parameter last | last = this.getParameter(this.getNumberOfParameters() - 1) |
       last.isParams() and
-      result = last.getType().(ArrayType).getElementType()
+      result = last.getType().(ParamsCollectionType).getElementType()
     )
   }
 
diff --git a/csharp/ql/lib/semmle/code/csharp/commons/Collections.qll b/csharp/ql/lib/semmle/code/csharp/commons/Collections.qll
index db38e7cb6ebb..a291c5dee4c4 100644
--- a/csharp/ql/lib/semmle/code/csharp/commons/Collections.qll
+++ b/csharp/ql/lib/semmle/code/csharp/commons/Collections.qll
@@ -2,6 +2,8 @@
 
 import csharp
 import semmle.code.csharp.frameworks.system.Collections
+private import semmle.code.csharp.frameworks.System
+private import semmle.code.csharp.frameworks.system.collections.Generic
 
 private string modifyMethodName() {
   result =
@@ -67,6 +69,39 @@ class CollectionType extends RefType {
   }
 }
 
+/**
+ * A collection type that can be used as a `params` parameter type.
+ */
+abstract private class ParamsCollectionTypeImpl extends ValueOrRefType {
+  abstract Type getElementType();
+}
+
+private class AddArrayType extends ParamsCollectionTypeImpl instanceof ArrayType {
+  override Type getElementType() { result = ArrayType.super.getElementType() }
+}
+
+private class AddCollectionTypes extends ParamsCollectionTypeImpl {
+  private ConstructedType base;
+
+  AddCollectionTypes() {
+    exists(UnboundGenericType unboundbase |
+      base = this.getABaseType*() and unboundbase = base.getUnboundGeneric()
+    |
+      unboundbase instanceof SystemCollectionsGenericIEnumerableTInterface or
+      unboundbase instanceof SystemCollectionsGenericICollectionInterface or
+      unboundbase instanceof SystemCollectionsGenericIListTInterface or
+      unboundbase instanceof SystemCollectionsGenericIReadOnlyCollectionTInterface or
+      unboundbase instanceof SystemCollectionsGenericIReadOnlyListTInterface or
+      unboundbase instanceof SystemSpanStruct or
+      unboundbase instanceof SystemReadOnlySpanStruct
+    )
+  }
+
+  override Type getElementType() { result = base.getTypeArgument(0) }
+}
+
+final class ParamsCollectionType = ParamsCollectionTypeImpl;
+
 /** Holds if `t` is a collection type. */
 predicate isCollectionType(ValueOrRefType t) {
   t.getABaseType*() instanceof SystemCollectionsIEnumerableInterface and
diff --git a/csharp/ql/lib/semmle/code/csharp/dispatch/Dispatch.qll b/csharp/ql/lib/semmle/code/csharp/dispatch/Dispatch.qll
index 1b27871d1ef6..080b7d5c7325 100644
--- a/csharp/ql/lib/semmle/code/csharp/dispatch/Dispatch.qll
+++ b/csharp/ql/lib/semmle/code/csharp/dispatch/Dispatch.qll
@@ -6,6 +6,7 @@
  */
 
 import csharp
+private import semmle.code.csharp.commons.Collections
 private import RuntimeCallable
 
 /** A call. */
@@ -1137,7 +1138,7 @@ private module Internal {
         if p.isParams()
         then (
           j >= i and
-          paramType = p.getType().(ArrayType).getElementType()
+          paramType = p.getType().(ParamsCollectionType).getElementType()
         ) else (
           i = j and
           paramType = p.getType()
diff --git a/csharp/ql/lib/semmle/code/csharp/frameworks/System.qll b/csharp/ql/lib/semmle/code/csharp/frameworks/System.qll
index ac16df764162..56e063b1b5e0 100644
--- a/csharp/ql/lib/semmle/code/csharp/frameworks/System.qll
+++ b/csharp/ql/lib/semmle/code/csharp/frameworks/System.qll
@@ -755,3 +755,19 @@ class SystemNotImplementedExceptionClass extends SystemClass {
 class SystemDateTimeStruct extends SystemStruct {
   SystemDateTimeStruct() { this.hasName("DateTime") }
 }
+
+/** The `System.Span<T>` struct. */
+class SystemSpanStruct extends SystemUnboundGenericStruct {
+  SystemSpanStruct() {
+    this.hasName("Span`1") and
+    this.getNumberOfTypeParameters() = 1
+  }
+}
+
+/** The `System.ReadOnlySpan<T>` struct. */
+class SystemReadOnlySpanStruct extends SystemUnboundGenericStruct {
+  SystemReadOnlySpanStruct() {
+    this.hasName("ReadOnlySpan`1") and
+    this.getNumberOfTypeParameters() = 1
+  }
+}
diff --git a/csharp/ql/lib/semmle/code/csharp/frameworks/system/collections/Generic.qll b/csharp/ql/lib/semmle/code/csharp/frameworks/system/collections/Generic.qll
index da41e09c3643..24c1277af026 100644
--- a/csharp/ql/lib/semmle/code/csharp/frameworks/system/collections/Generic.qll
+++ b/csharp/ql/lib/semmle/code/csharp/frameworks/system/collections/Generic.qll
@@ -158,3 +158,21 @@ class SystemCollectionsGenericIDictionaryInterface extends SystemCollectionsGene
     this.getNumberOfTypeParameters() = 2
   }
 }
+
+/** The ``System.Collections.Generic.IReadOnlyCollection`1`` interface. */
+class SystemCollectionsGenericIReadOnlyCollectionTInterface extends SystemCollectionsGenericUnboundGenericInterface
+{
+  SystemCollectionsGenericIReadOnlyCollectionTInterface() {
+    this.hasName("IReadOnlyCollection`1") and
+    this.getNumberOfTypeParameters() = 1
+  }
+}
+
+/** The ``System.Collections.Generic.IReadOnlyList`1`` interface. */
+class SystemCollectionsGenericIReadOnlyListTInterface extends SystemCollectionsGenericUnboundGenericInterface
+{
+  SystemCollectionsGenericIReadOnlyListTInterface() {
+    this.hasName("IReadOnlyList`1") and
+    this.getNumberOfTypeParameters() = 1
+  }
+}